Gradient tinted articles and methods of making the same

ABSTRACT

A glass-ceramic, includes a silicate-containing glass comprising a first portion and a second portion. A plurality of crystalline precipitates comprising at least one of W and Mo. The crystalline precipitates are distributed within at least one of the first and second portions of the silicate-containing glass. The glass-ceramic comprises a difference in absorbance between the first and second portions of 0.04 optical density (OD)/mm or greater over a wavelength range of from 400 nm to 1500 nm.

This application is a divisional and claims the benefit of priority ofU.S. patent application Ser. No. 16/778,867, filed on Jan. 31, 2020,which claims the benefit of priority to U.S. Provisional ApplicationSer. No. 62/804,275 filed on Feb. 12, 2019, the content of which isrelied upon and incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to tinted articles, and morespecifically, to compositions and methods of forming gradient tintedglass and glass-ceramic articles.

BACKGROUND

Transparent and translucent articles may be colored and/or tinted for avariety of reasons. Tinting is accomplished by modifying the opticalabsorbance of the transparent article. Modification of the opticalabsorbance of an article often requires extensive additional processsteps (e.g., the deposition of opaque material), use of dyedinterlayers, and/or secondary processes such as etching or lasermarking. The generation of gradients, indicia and/or other controlledchanges in the optical absorbance of the article according to theseapproaches present a variety of technically challenging issues.Additionally, the processes necessary to produce a range of color orabsorbance in colored glass and glass-ceramics have typically required agradient furnace or additional thermal treatments. The use of a gradientfurnace is typically more costly than conventional processes that employan isothermal furnace.

As such, the development of a single material composition that can beprocessed during conventional fabrication approaches (i.e., without theneed for any post-processing or other additional process steps) toproduce a range of colors, while selectively controlling a desired levelof transmittance may be advantageous.

SUMMARY OF THE DISCLOSURE

According to at least one feature of the present disclosure, aglass-ceramic is provided that includes a silicate-containing glasscomprising a first portion and a second portion. A plurality ofcrystalline precipitates comprising at least one of W and Mo. Thecrystalline precipitates are distributed within at least one of thefirst and second portions of the silicate-containing glass. Theglass-ceramic comprises a difference in absorbance between the first andsecond portions of 0.04 optical density (OD)/mm or greater over awavelength range of from 400 nm to 1500 nm.

According to another feature of the present disclosure, a method offorming a glass-ceramic article is provided that includes: forming aglass substrate having a substantially homogenous bulk composition,wherein the glass substrate comprises a first portion and a secondportion; and variably crystallizing at least one of the first and secondportions of the substrate to form a plurality of crystallineprecipitates within the at least one of the first and second portions,wherein the variably crystallizing of the at least one of the first andsecond portions results in at least one of: (a) a difference inabsorbance between the first and second portions of 0.04 OD/mm to 49OD/mm over a wavelength range of from 400 nm to 750 nm, and (b) adifference in absorbance between the first and second portions of 0.03OD/mm to 0.69 OD/mm over a wavelength range of from 750 nm to 1500 nm.

According to another feature of the present disclosure, a method offorming a glass-ceramic article is provided that includes: forming aglass substrate having a substantially homogenous bulk composition,wherein the glass substrate comprises a first portion and a secondportion; and thermally processing the first and second portions of thesubstrate at one or more of (a) different temperatures, (b) differentheating rates and (c) different times, wherein the thermally processingstep is conducted to form the glass-ceramic article and generate aplurality of crystalline precipitates in at least one of the first andsecond portions of the substrate such that (i) a difference inabsorbance exists between the first and second portions of 0.04 OD/mm to49 OD/mm over a wavelength range of from 400 nm to 750 nm and (ii) aContrast Ratio between the first portion and the second portion is from1.4 to 165 over a wavelength range of from 400 nm to 700 nm.

According to a first embodiment, a glass-ceramic is provided thatincludes: a silicate-containing glass comprising a first portion and asecond portion; and a plurality of crystalline precipitates comprisingat least one of W and Mo, wherein the crystalline precipitates aredistributed within at least one of the first and second portions of thesilicate-containing glass, wherein the glass-ceramic comprises adifference in absorbance between the first and second portions of 0.04optical density (OD)/mm or greater over a wavelength range of from 400nm to 1500 nm.

According to a second embodiment, the first embodiment is provided,wherein the plurality of crystalline precipitates comprise an oxide ofthe chemical form of one or more of M_(x)WO₃ and M_(x)MoO₃, wherein M isone or more of H, Li, Na, K, Rb, Cs, Ca, Sr, Ba, Zn, Ag, Au, Cu, Sn, Cd,In, Tl, Pb, Bi, Th, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, andU, and 0<x<1.

According to a third embodiment, the first or the second embodiment isprovided that further includes: one or more of WO₃ and MoO₃ from 0 mol %to 15 mol % in total.

According to a fourth embodiment, any one of the first through the thirdembodiment is provided that further includes: at least one of: (i) Aufrom 0.001 mol % to 0.5 mol %, (ii) Ag from 0.025 mol % to 1.5 mol %,and (iii) Cu from 0.03 mol % to 1 mol %.

According to a fifth embodiment, any one of the first through the thirdembodiment is provided that further includes: at least one of: (i) Aufrom 0.001 mol % to 0.5 mol %, (ii) Ag from 0.1 mol % to 1 mol %, and(iii) Cu from 0.03 mol % to 1 mol %.

According to a sixth embodiment, any one of the first through the fifthembodiments is provided, wherein the plurality of crystallineprecipitates comprises non-stoichiometric tungsten suboxides, andfurther wherein the plurality of crystalline precipitates isintercalated with dopant cations selected from the group of transitionmetals consisting of Ag, Au and Cu.

According to a seventh embodiment, any one of the first through thesixth embodiments is provided, wherein a Contrast Ratio between thefirst portion and the second portion is from 1.4 to 165 over awavelength range of from 400 nm to 700 nm.

According to an eighth embodiment, any one of the first through thesixth embodiments is provided, wherein a Contrast Ratio between thefirst portion and the second portion is from 1.5 to 14 over a wavelengthrange of from 750 nm to 1500 nm.

According to a ninth embodiment, any one of the first through the sixthembodiments is provided, wherein the difference in absorbance betweenthe first and second portions is from 0.04 OD/mm to 49 OD/mm over awavelength range of from 400 nm to 750 nm.

According to a tenth embodiment, any one of the first through the ninthembodiments is provided that further includes: V₂O₅ from 0.0001 mol % to0.5 mol %.

According to an eleventh embodiment, a method of forming a glass-ceramicarticle is provided that includes: forming a substrate having asubstantially homogenous glass composition, wherein the substratecomprises a first portion and a second portion; and variablycrystallizing at least one of the first and second portions of thesubstrate to form a plurality of crystalline precipitates within the atleast one of the first and second portions. Further, the variablycrystallizing of the at least one of the first and second portionsresults in at least one of: (a) a difference in absorbance between thefirst and second portions of 0.04 OD/mm to 49 OD/mm over a wavelengthrange of from 400 nm to 750 nm, and (b) a difference in absorbancebetween the first and second portions of 0.03 OD/mm to 0.69 OD/mm over awavelength range of from 750 nm to 1500 nm.

According to a twelfth embodiment, the eleventh embodiment is provided,wherein the step of variably crystallizing further comprises thermallyprocessing the first and second portions of the substrate at differenttemperatures.

According to a thirteenth embodiment, the eleventh embodiment isprovided, wherein the step of variably crystallizing further comprisesthermally processing the first and second portions of the substrate atthe same temperature and cooling the first and second portions atdifferent cooling rates

According to a fourteenth embodiment, the eleventh or twelfth embodimentis provided, wherein the step of variably crystallizing furthercomprises increasing the temperature of the first and second portions atdifferent heating rates.

According to a fifteenth embodiment, a method of forming a glass-ceramicis provided that includes: forming a substrate having a substantiallyhomogenous glass composition, wherein the substrate comprises a firstportion and a second portion; and thermally processing the first andsecond portions of the substrate at one or more of (a) differenttemperatures, (b) different heating rates and (c) different times.Further, the thermally processing step is conducted to generate aplurality of crystalline precipitates in at least one of the first andsecond portions of the substrate such that (i) a difference inabsorbance exists between the first and second portions of 0.04 OD/mm to49 OD/mm over a wavelength range of from 400 nm to 750 nm and (ii) aContrast Ratio between the first portion and the second portion is from1.4 to 165 over a wavelength range of from 400 nm to 700 nm.

According to a sixteenth embodiment, the fifteenth embodiment isprovided, wherein the glass-ceramic article further comprises WO₃ from 0mol % to 15 mol %.

According to a seventeenth embodiment, the fifteenth embodiment isprovided, wherein the WO₃ is from 0 mol % to 7 mol %.

According to an eighteenth embodiment, any one of the fifteenth throughthe seventeenth embodiments is provided, wherein the glass-ceramicarticle further comprises MoO₃ from 0 mol % to 15 mol %.

According to a nineteenth embodiment, the eighteenth embodiment isprovided, wherein the MoO₃ is from 0 mol % to 7 mol %.

According to a twentieth embodiment, any one of the fifteenth throughthe nineteenth embodiments is provided, wherein the step of thermallyprocessing the first and second portions of the substrate is conductedsuch that the first and second portions are subjected to a temperaturegreater than 400° C. for different times.

These and other features, advantages, and objects of the presentdisclosure will be further understood and appreciated by those skilledin the art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a description of the figures in the accompanyingdrawings. The figures are not necessarily to scale, and certain featuresand certain views of the figures may be shown exaggerated in scale or inschematic in the interest of clarity and conciseness.

In the drawings:

FIG. 1 is a cross-sectional view of an article, according to at leastone example of the disclosure;

FIG. 2 is a schematic flowchart of a method, according to at least oneexample;

FIGS. 3A and 3B are images taken of a plurality of wafers after heattreating followed by a controlled cooling;

FIG. 3C is a plot of absorbance vs wavelength for sample 2 of FIGS. 3Aand 3B;

FIG. 3D is a plot of absorbance vs wavelength for sample 3 of FIGS. 3Aand 3B;

FIG. 4A is an image of a wafer cooling in air after a heat treating;

FIG. 4B is an image of the wafer of FIG. 4A placed on a light table tohighlight the contrast difference across the wafer;

FIG. 4C is a plot of the temperature of a wafer and a metal washer vs.time after a heat treating for a sample consistent with FIG. 4A;

FIG. 5A is an image of a wafer with a graphite part cooling after heattreatment;

FIG. 5B is an image of the wafer of FIG. 5A positioned on a light tablewith the graphite part removed;

FIG. 6A is an image of a wafer with a plurality of metal washers coolingafter heat treatment;

FIG. 6B is an image of the wafer of FIG. 6A positioned on a light tablewith the metal washers removed;

FIG. 7A is an image of a plurality of wafers positioned on a light tablewith their associated metallized letters used in a heat treatment;

FIG. 7B is a plot of absorbance vs wavelength for regions E and F ofFIG. 7A;

FIGS. 8A and 8B are images of wafers on light tables on which strips ofaluminum foil were placed during heat treating;

FIG. 9A is an image of a wafer on which a metal nut was placed duringheat treatment;

FIG. 9B is a plot of absorbance vs wavelength for the wafer of FIG. 9A;

FIG. 10A is an image of a wafer on which a preheated metal washer wasplaced;

FIG. 10B is a plot of absorbance vs wavelength for the wafer of FIG.10A;

FIG. 11A is an image of a wafer on which a preheated washer was placed;

FIG. 11B is a plot of absorbance vs wavelength for the wafer of FIG.11A;

FIG. 12A is an image of a wafer in accordance with embodiments of thedisclosure;

FIG. 12B is a plot of transmittance vs. wavelength for the wafer of FIG.12A;

FIGS. 13A-13E are images of a heat sink in accordance with embodimentsof the disclosure;

FIG. 14A is an image of a wafer in accordance with embodiments of thedisclosure; and

FIG. 14B is a plot of transmittance vs. wavelength for the wafer of FIG.14A.

DETAILED DESCRIPTION

Additional features and advantages of the invention will be set forth inthe detailed description which follows and will be apparent to thoseskilled in the art from the description, or recognized by practicing theinvention as described in the following description, together with theclaims and appended drawings.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

In this document, relational terms, such as first and second, top andbottom, and the like, are used solely to distinguish one entity oraction from another entity or action, without necessarily requiring orimplying any actual such relationship or order between such entities oractions.

Modifications of the disclosure will occur to those skilled in the artand to those who make or use the disclosure. Therefore, it is understoodthat the embodiments shown in the drawings and described above aremerely for illustrative purposes and not intended to limit the scope ofthe disclosure, which is defined by the following claims, as interpretedaccording to the principles of patent law, including the doctrine ofequivalents.

It will be understood by one having ordinary skill in the art thatconstruction of the described disclosure, and other components, is notlimited to any specific material. Other exemplary embodiments of thedisclosure disclosed herein may be formed from a wide variety ofmaterials, unless described otherwise herein.

For purposes of this disclosure, the term “coupled” (in all of itsforms: couple, coupling, coupled, etc.) generally means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents. Such joining may be permanent in nature, or may be removableor releasable in nature, unless otherwise stated.

As used herein, the term “about” means that amounts, sizes,formulations, parameters, and other quantities and characteristics arenot and need not be exact, but may be approximate and/or larger orsmaller, as desired, reflecting tolerances, conversion factors, roundingoff, measurement error and the like, and other factors known to those ofskill in the art. When the term “about” is used in describing a value oran end-point of a range, the disclosure should be understood to includethe specific value or end-point referred to. Whether or not a numericalvalue or end-point of a range in the specification recites “about,” thenumerical value or end-point of a range is intended to include twoembodiments: one modified by “about,” and one not modified by “about.”It will be further understood that the end-points of each of the rangesare significant both in relation to the other end-point, andindependently of the other end-point.

Unless otherwise specified, all compositions are expressed in terms ofas-batched mole percent (mol %). As will be understood by those havingordinary skill in the art, various melt constituents (e.g., fluorine,alkali metals, boron, etc.) may be subject to different levels ofvolatilization (e.g., as a function of vapor pressure, melt time and/ormelt temperature) during melting of the constituents. As such, the term“about,” in relation to such constituents, is intended to encompassvalues within about 0.2 mol % when measuring final articles as comparedto the as-batched compositions provided herein. With the foregoing inmind, substantial compositional equivalence between final articles andas-batched compositions is expected.

For purposes of this disclosure, the terms “bulk,” “bulk composition”and/or “overall compositions” are intended to include the overallcomposition of the entire article, which may be differentiated from a“local composition” or “localized composition” which may differ from thebulk composition owing to the formation of crystalline and/or ceramicphases.

As also used herein, the terms “article,” “glass-article,”“ceramic-article,” “glass-ceramics,” “glass elements,” “glass-ceramicarticle” and “glass-ceramic articles” may be used interchangeably, andin their broadest sense, to include any object made wholly or partly ofglass and/or glass-ceramic material.

As used herein, a “glass state” refers to an inorganic amorphous phasematerial within the articles of the disclosure that is a product ofmelting that has cooled to a rigid condition without crystallizing. Asused herein, a “glass-ceramic state” refers to an inorganic materialwithin the articles of the disclosure which includes both the glassstate and a “crystalline phase” and/or “crystalline precipitates” asdescribed herein.

As used herein, “transmission”, “transmittance”, “optical transmittance”and “total transmittance” are used interchangeably in the disclosure andrefer to external transmission or transmittance, which takes absorption,scattering and reflection into consideration. Fresnel reflection is notsubtracted out of the transmission and transmittance values reportedherein. In addition, any total transmittance values referenced over aparticular wavelength range are given as an average of the totaltransmittance values measured over the specified wavelength range.

As used herein, “optical density units”, “OD” and “OD units” are usedinterchangeably in the disclosure to refer to optical density units, ascommonly understood as a measure of absorbance of the material tested,as measured with a spectrometer given by OD=−log (I/I₀) where I₀ is theintensity of light incident on the sample and I is the intensity oflight that is transmitted through the sample. Further, the terms “OD/mm”or “OD/cm” used in this disclosure are normalized measures ofabsorbance, as determined by dividing the optical density units (i.e.,as measured by an optical spectrometer) by the thickness of the sample(e.g., in units of millimeters or centimeters). In addition, any opticaldensity units referenced over a particular wavelength range (e.g., 3.3OD/mm to 24.0 OD/mm in UV wavelengths from 280 nm to 380 nm) are givenas an average value of the optical density units over the specifiedwavelength range.

Referring now to FIG. 1, an article 10 is depicted that includes asubstrate 14 having a glass and/or glass-ceramic composition accordingto the disclosure. The article 10 can be employed in any number ofapplications. For example, the article 10 and/or substrate 14 can beemployed in the form of substrates, elements, covers and other elementsin any number of optics related and/or aesthetic applications.

The substrate 14 defines or includes a pair of opposing primary surfaces18, 22. In some examples of the article 10, the substrate 14 includes acompressive stress region 26. As shown in FIG. 1, the compressive stressregion 26 extends from the primary surface 18 to a first selected depth30 in the substrate 14. In some examples, the substrate 14 includes acomparable compressive stress region 26 that extends from the primarysurface 18 to a second selected depth. Further, in some examples,multiple compressive stress regions 26 may extend from the primarysurfaces 18, 22 and/or edges of the substrate 14. The substrate 14 mayhave a selected length and width, or diameter, to define its surfacearea. The substrate 14 may have at least one edge between the primarysurfaces 18, 22 of the substrate 14 defined by its length and width, ordiameter. The substrate 14 may also have a selected thickness. Accordingto various examples, the substrate 14 may include a first portion 34 anda second portion 38. It will be understood that although described asincluding two portions, the substrate 14 may include any number ofportions. As will be explained in greater detail below, the firstportion 34 and the second portion 38 may exhibit different opticalproperties (e.g., transmittance, color, optical density, etc.) and/ordifferent mechanical properties (e.g., depth of compression, strength,hardness, etc.). By altering the number of portions and opticalproperties of the various portions, various optical effects (e.g.,gradient tints, gradient colors, patterns, etc.) may be achieved.

It will be understood that where a specific attribute, feature,functionality and/or property (e.g., optical or mechanical property) isdescribed in connection with the article 10 generally, one, both orneither of the first portion 34 and the second portion 38 may includethe feature, attribute and/or property. Further, it will be understoodthat while described herein as including “portions,” such a descriptionof the substrate 14 may simply be a manner of describing the opticalchange exhibited across the article 10 or substrate 14 and notnecessarily indicative of a quantized region of the article 10 orsubstrate 14 exhibiting such a property.

As used herein, a “selected depth,” (e.g., selected depth 30) “depth ofcompression” and “DOC” are used interchangeably to define the depth atwhich the stress in the substrate 14, as described herein, changes fromcompressive to tensile. DOC may be measured by a surface stress meter,such as an FSM-6000, or a scattered light polariscope (SCALP) dependingon the ion exchange treatment. Where the stress in a substrate 14 havinga glass or a glass-ceramic composition is generated by exchangingpotassium ions into the glass substrate 14, a surface stress meter isused to measure DOC. Where the stress is generated by exchanging sodiumions into the glass substrate 10, SCALP is used to measure DOC. Wherethe stress in the substrate 14 having a glass or glass-ceramiccomposition is generated by exchanging both potassium and sodium ionsinto the glass, the DOC is measured by SCALP, since it is believed theexchange depth of sodium indicates the DOC and the exchange depth ofpotassium ions indicates a change in the magnitude of the compressivestress (but not the change in stress from compressive to tensile); theexchange depth of potassium ions in such glass substrates 14 is measuredby a surface stress meter. As also used herein, the “maximum compressivestress” is defined as the maximum compressive stress within thecompressive stress region 26 in the substrate 14. In some examples, themaximum compressive stress is obtained at or in close proximity to theone or more primary surfaces 18, 22 defining the compressive stressregion 26. In other examples, the maximum compressive stress is obtainedbetween the one or more primary surfaces 18, 22 and the selected depth30 of the compressive stress region 26.

In some examples of the article 10, as depicted in exemplary form inFIG. 1, the substrate 14 is selected from a chemically strengthenedalumino-boro-silicate glass or glass-ceramic. For example, the substrate14 can be selected from chemically strengthened alumino-boro-silicateglass or glass-ceramic having a compressive stress region 26 extendingto a first selected depth 30 of greater than 10 μm, with a maximumcompressive stress of greater than 150 MPa. In further examples, thesubstrate 14 is selected from a chemically strengthenedalumino-boro-silicate glass or glass-ceramic having a compressive stressregion 26 extending to a first selected depth 30 of greater than 25 μm,with a maximum compressive stress of greater than 400 MPa. The substrate14 of the article 10 may also include one or more compressive stressregions 26 that extend from one or more of the primary surfaces 18, 22to a selected depth 30 (or depths) having a maximum compressive stressof greater than about 150 MPa, greater than 200 MPa, greater than 250MPa, greater than 300 MPa, greater than 350 MPa, greater than 400 MPa,greater than 450 MPa, greater than 500 MPa, greater than 550 MPa,greater than 600 MPa, greater than 650 MPa, greater than 700 MPa,greater than 750 MPa, greater than 800 MPa, greater than 850 MPa,greater than 900 MPa, greater than 950 MPa, greater than 1000 MPa, andall maximum compressive stress levels between these values. In someexamples, the maximum compressive stress is 2000 MPa or lower. In otherexamples, the compressive stress regions 26 have a maximum compressivestress from about 150 MPa to about 2000 MPa, or from about 150 MPa toabout 1500 MPa, or from about 150 MPa to about 1000 MPa. Further, thecompressive stress regions 26 can have any and all values and rangesbetween these specified maximum compressive stress values. In addition,the depth of compression (DOC) or first selected depth 30 can be set at10 μm or greater, 15 μm or greater, 20 μm or greater, 25 μm or greater,30 μm or greater, 35 μm or greater, and to even higher depths, dependingon the thickness of the substrate 14 and the processing conditionsassociated with generating the compressive stress region 26. In someexamples, the DOC is less than or equal to 0.3 times the thickness (t)of the substrate 14, for example 0.3 t, 0.28 t, 0.26 t, 0.25 t, 0.24 t,0.23 t, 0.22 t, 0.21 t, 0.20 t, 0.19 t, 0.18 t, 0.15 t, or 0.10 t andall values therebetween.

As will be explained in greater detail below, the article 10 is formedfrom an as-batched composition and is cast in a glass state. The article10 may later be annealed and/or thermally processed (e.g., heat treated)to form a glass-ceramic state having a plurality of ceramic orcrystalline particles. It will be understood that depending on thecasting technique employed, the volume of glass cast and the geometry ofthe casting, the article 10 may readily crystallize and become aglass-ceramic without additional heat treatment (e.g., essentially becast into the glass-ceramic state). In examples where a post-formingthermal processing is employed, a portion, a majority, substantially allor all of the article 10 may be converted from the glass-state to theglass-ceramic state. For example, the first portion 34 and the secondportion 38 may exhibit different quantities of crystallization and/orcrystals of different sizes and/or chemistries. As such, althoughcompositions of the article 10 may be described in connection with theglass state and/or the glass-ceramic state, the bulk composition of thearticle 10 may remain substantially unaltered when converted between theglass and glass-ceramic states, despite localized portions of thearticle 10 having a different composition (i.e., owing to the formationof the ceramic or crystalline precipitates). Further, it will beunderstood that while the compositions are described in terms of anas-batched state, one having ordinary skill in the art will recognizewhich constituents of the article 10 may volatize in the melting process(i.e., and therefore be less present in the article 10 relative to theas-batched composition) and others which will not.

According to various examples, the article 10 may include Al₂O₃, SiO₂,B₂O₃, WO₃, MO₃, Ag, Au, Cu, V₂O₅, R₂O where R₂O is one or more of Li₂O,Na₂O, K₂O, Rb₂O and Cs₂O, RO where RO is one or more of MgO, CaO, SrO,BaO and ZnO and a number of dopants.

Unless otherwise noted, glass compositions correspond to as-batched molepercentage (mol %) in a crucible for melting.

The article 10 may have from about 40 mol % to about 80 mol % SiO₂, orfrom about 50 mol % to about 75 mol % SiO₂ or from about 60 mol % toabout 72 mol % SiO₂. For example, the article 10 may have about 42 mol%, about 44 mol %, about 46 mol %, about 48 mol %, about 50 mol %, about52 mol %, about 54 mol %, about 56 mol %, about 58 mol %, about 60 mol%, about 62 mol %, about 64 mol %, about 66 mol %, about 68 mol %, about70 mol %, about 72 mol %, about 74 mol %, about 76 mol % or about 78 mol% SiO₂. It will be understood that any and all values and ranges betweenthe above-noted ranges of SiO₂ are contemplated.

The article 10 may include from about 1 mol % to about 20 mol % Al₂O₃,or from about 7 mol % to about 20 mol % Al₂O₃, or from about 1 mol % toabout 15 mol % Al₂O₃, or from about 5 mol % to about 15 mol % Al₂O₃, orfrom about 7 mol % to about 15 mol % Al₂O₃, or from about 7 mol % toabout 12 mol % Al₂O₃. For example, the article 10 may have about 2 mol%, about 3 mol %, about 4 mol %, about 5 mol %, about 6 mol %, about 7mol %, about 8 mol %, about 9 mol %, about 10 mol %, about 11 mol %,about 12 mol %, about 13 mol % or about 14 mol % Al₂O₃. It will beunderstood that any and all values and ranges between the above-notedranges of Al₂O₃ are contemplated.

The article 10 may include WO₃ and/or MoO₃. The combined amount of WO₃and MoO₃ is referred to herein as “WO₃ plus MoO₃” where it is understoodthat “WO₃ plus MoO₃” refers to WO₃ alone, MoO₃ alone, or a combinationof WO₃ and MoO₃. For example, WO₃ plus MoO₃ may be from about 1 mol % toabout 18 mol %, or from about 2 mol % to about 10 mol %, or from about3.5 mol % to about 8 mol % or from about 3 mol to about 6 mol %. Withrespect to MoO₃, the article 10 may have from about 0 mol % to about 15mol % MoO₃, or from about 0 mol % to about 7 mol % MoO₃, or from about 0mol % to about 4 mol % MoO₃. For example, the article 10 may have about1 mol %, about 2 mol %, about 3 mol %, about 4 mol %, about 5 mol %,about 6 mol %, about 7 mol %, about 8 mol %, about 9 mol %, about 10 mol%, about 11 mol %, about 12 mol %, about 13 mol %, about 14 mol % MoO₃.With respect to WO₃, the article 10 may have from about 0 mol % to about15 mol % WO₃, or from about 0 mol % to about 7 mol % WO₃, or from about0 mol % to about 4 mol % WO₃. For example, the article 10 may have about1 mol %, about 2 mol %, about 3 mol %, about 4 mol %, about 5 mol %,about 6 mol %, about 7 mol %, about 8 mol %, about 9 mol %, about 10 mol%, about 11 mol %, about 12 mol %, about 13 mol %, about 14 mol % WO₃.It will be understood that any and all values and ranges between theabove-noted ranges of WO₃ plus MoO₃, WO₃ and/or MoO₃ are contemplated.

The article 10 may include from about 3 mol % to about 50 mol % B₂O₃, orfrom about 5 mol % to about 50 mol % of B₂O₃, or from about 5 mol % toabout 25 mol % B₂O₃, or from about 8 mol % to about 15 mol % B₂O₃. Forexample, the article 10 may include about 3 mol %, 4 mol %, 5 mol %, 10mol %, 15 mol %, 20 mol %, 25 mol %, 30 mol %, 35 mol %, 40 mol %, 45mol %, or about 50 mol % B₂O₃. It will be understood that any and allvalues and ranges between the above-noted ranges of B₂O₃ arecontemplated.

The article 10 may include at least one alkali metal oxide. The alkalimetal oxide may be represented by the chemical formula R₂O where R₂O isone or more of Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O and/or combinations thereof.The article 10 may have R₂O from about 0 mol % to about 15 mol %, orfrom about 3 mol % to about 14 mol % or from about 7 mol % to about 12mol % R₂O. For example, the article 10 may have about 1 mol %, about 2mol %, about 3 mol %, about 4 mol %, about 5 mol %, about 6 mol %, about7 mol %, about 8 mol %, about 9 mol %, about 10 mol %, about 11 mol %,about 12 mol %, about 13 mol % or about 14 mol % R₂O. It will beunderstood that any and all values and ranges between the above-notedranges of R₂O are contemplated.

According to various examples, R₂O minus Al₂O₃ (i.e., the differencebetween the amount of R₂O and Al₂O₃) ranges from about from about −12mol % to about 4 mol %, or from about −12 mol % to about 3.8 mol %, orfrom about −10 mol % to about 3.5 mol %, or from about −8 mol % to about3 mol %, or from about −6 mol % to about 1.5 mol %. For example, thearticle 10 can include R₂O minus Al₂O₃ of about −12 mol %, −11 mol %,−10 mol %, −9 mol %, −8 mol %, −7 mol %, −6 mol %, −5 mol %, −4 mol %,−3 mol %, −2 mol %, −1 mol %, 0 mol %, +1 mol %, +2 mol %, +3 mol %, orabout +4 mol %. It will be understood that any and all values and rangesbetween the above-noted ranges of R₂O minus Al₂O₃ are contemplated. Thedifference in R₂O and Al₂O₃ specified herein influences the availabilityof excess alkali cations to interact with tungsten and/or molybdenumoxide, thereby modulating/controlling the formation of alkali tungstenbronzes (e.g. non-stoichiometric tungsten sub-oxides), stoichiometricalkali tungstates (e.g., Na₂WO₄), alkali molybdenum bronzes (e.g.non-stoichiometric molybdenum sub-oxides) and/or stoichiometric alkalimolybdeates.

The article 10 may include at least one alkaline earth metal oxideand/or ZnO. The alkaline earth metal oxide may be represented by thechemical formula RO where RO is one or more of MgO, CaO, SrO, and BaO.The article 10 may include RO from about 0 mol % to about 15 mol % RO,or from about 3 mol % to about 14 mol % RO, or from about 0.01 mol % toabout 2 mol % RO, or from about 0 mol % to about 0.5 mol % RO. Forexample, the article 10 may include about 0 mol %, about 1 mol %, about2 mol %, about 3 mol %, about 4 mol %, about 5 mol %, about 6 mol %,about 7 mol %, about 8 mol %, about 9 mol %, about 10 mol %, about 11mol %, about 12 mol %, about 13 mol %, about 14 mol %, or about 15 mol %RO. The article 10 may include ZnO from about 0 mol % to about 15 mol %ZnO, or from about 3 mol % to about 14 mol % ZnO, or from about 0 mol %to about 0.5 mol % ZnO. It will be understood that any and all valuesand ranges between the above-noted ranges of RO and ZnO arecontemplated. According to various examples, the amount of R₂O may begreater than the amount of RO and/or ZnO. Further, the article 10 may befree of RO and/or ZnO.

The article 10 may include from about 0 mol % to about 0.5 mol % ofSnO₂, or from about 0.05 mol % to about 2 mol % of SnO₂. For example,the article 10 can include about 0 mol %, about 0.01 mol %, about 0.05mol %, about 0.1 mol %, about 0.5 mol %, about 1 mol %, about 1.5 mol %,or about 2 mol % of SnO₂. The article 10 may include from about 0.01 mol% to about 1.5 mol % Cu, or from about 0.05 mol % to about 1.0 mol % Cuor from about 0.1 mol % to about 0.5 mol % Cu. The article 10 mayinclude from about 0.0001 mol % V₂O₅, or from about 0.0005 mol % toabout 0.5 mol % V₂O₅, or from about 0.001 mol % to about 0.1 mol % V₂O₅or from about 0.001 mol % to about 0.005 V₂O₅. The article 10 mayinclude from about 0.05 mol % to about 1.5 mol % Ag, or from about 0.1mol % to about 1.0 mol % Ag or from about 0.25 mol % to about 0.6 mol %Ag. It will be understood that any and all values and ranges between theabove-noted ranges of SnO₂, Cu, V₂O₅ or Ag are contemplated. Forexample, the article 10 may include at least one of: (i) Au from about0.001 mol % to about 0.5 mol %, (ii) Ag from about 0.025 mol % to about1.5 mol %, and (iii) Cu from about 0.03 mol % to about 1.0 mol %. Itwill be understood that Ag, Au and/or Cu may exist within the article 10at any oxidation state and/or in a combination of oxidation states inthe above-noted mol % values.

According to various examples, the article 10 can further include atleast one dopant selected from the group consisting of Ti, V, Cr, Mn,Fe, Co, Ni, Se, Nb, Mo, Tc, Ru, Rh, Pd, Cd, Te, Ta, Re, Os, Ir, Pt, Ti,Pb, Bi, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and/or Lu toalter the ultraviolet, visual, color and/or near-infrared absorbance.The dopants may have a concentration of from about 0.0001 mol % to about1.0 mol % within the glass composition. In some examples, Ag, Au and/orCu may be dopants.

It will be understood that each of the above noted compositions andcomposition ranges for SiO₂, Al₂O₃, WO₃, MoO₃, WO₃ plus MoO₃, B₂O₃, R₂O,RO, V₂O₅, Ag, Au, Cu, SnO₂, and dopants may be used with any othercomposition and/or composition range of the other constituents of theglass as outlined herein. For example, Tables 1, 2 and 3 provideexemplary composition ranges of the article 10 in an as-batched mol %.

TABLE 1 Constituent Min. Max. SiO₂ 40 80 Al₂O₃ 1 15 B₂O₃ 5 50 R₂O 0 15RO 0 2 ZnO 0 2 P₂O₅ 0 3 MoO₃ 0 15 WO₃ 1 15 SnO₂ 0 0.5 Ag 0 1.5 Au 0 0.5Cu 0 1 CeO₂ 0 1 MoO₃ plus 1 18 WO₃ R₂O minus −12 5 Al₂O₃

TABLE 2 Constituent Min. Max. SiO₂ 50 75 Al₂O₃ 5 15 B₂O₃ 6 25 R₂O 3 14RO 0 1 ZnO 0 1 P₂O₅ 0 2 MoO₃ 0 7 WO₃ 2 7 SnO₂ 0.01 0.4 Ag 0 1 Au 0 0.4Cu 0 0.95 CeO₂ 0. 0.5 MoO₃ plus WO₃ 2 8 R₂O minus Al₂O₃ −8 3.5

TABLE 3 Constituent Min. Max. SiO₂ 60 72 Al₂O₃ 7 12 B₂O₃ 8 15 R₂O 7 12RO 0 0.5 ZnO 0 0.5 P₂O₅ 0 1.5 MoO₃ 0 4 WO₃ 3 4 SnO₂ 0.05 0.3 Ag 0 0.5 Au0 0.3 Cu 0 0.85 CeO₂ 0 0.25 MoO₃ plus WO₃ 3 6 R₂O minus Al₂O₃ 0 0.75

Table 4 provides a list of exemplary properties of the article 10 in anun-doped state (e.g., where Cu, Ag, Au and V are considered dopants andno other dopants are included). The data of Table 4 corresponds to thearticle 10 having the composition outlined in as example 31 below.

TABLE 4 Property Value Strain Point (° C.) 455° Anneal Point (° C.)499.6 Softening Point (° C.) 723.2 Expansion (10⁻⁷/° C.) 60.3 Density at4° C. (g/cm³) 2.509 Liquidus Temperature (° C.) 970

Table 5 provides exemplary viscosity values at standard points for ofthe article 10 in an un-doped state (e.g., where Cu, Ag, Au and V areconsidered dopants and no other dopants are included). The data of Table5 corresponds to the article 10 having the composition outlined in asexample 31 below.

TABLE 5 Temperature Viscosity (° C.) (Poise) 974.8 125833 1011.8 676291049.3 37407 1087.1 21447 1129.4 11992 1165.9 7493 1203.3 4741 1240.83054 1278.9 2007 1317.5 1323 1356.8 886 1416.5 524 1457.6 357 1499.8 2461527.7 200

As explained below, conventional formation of tungsten-, molybdenum-, ormixed tungsten molybdenum-containing alkali glasses has been hampered bythe separation of the melt constituents during the melting process. Theseparation of the glass constituents during the melting process resultedin a perceived solubility limit of of the oxides of tungsten andmolybdenum within the molten glass, and therefore of articles cast fromsuch melts. Conventionally, when a tungsten, molybdenum, or mixedtungsten-molybdenum-dopedalkali-alumino-borosilicate glass wasformulated such that it was even slightly peralkaline (e.g., R₂O minusAl₂O₃=about 0.25 mol % or greater), the melt formed both a glass and adense alkali tungstate, alkali molybdate, and or mixed alkalitungsto-molybdate liquid second phase. While the concentration of thealkali tungstate second phase could be minimized by thorough mixing,melting at a high temperature, and employing a small batch size (˜1000g), it could not be fully eliminated leading to formation of adeleterious second crystalline phase. It is believed that the formationof this alkali tungstate phase occurs in the initial stages of the melt,where tungsten and/or molybdenum oxide reacts with “free” or “unbound”alkali carbonates. Due to the high density of alkali tungstate and/oralkali molybdate relative to the borosilicate glass that is formed, itrapidly segregates and/or stratifies, pooling at the bottom of thecrucible and does not rapidly solubilize in the glass due to thesignificant difference in density. As the R₂O constituents may providebeneficial properties to the glass composition, simply decreasing thepresence of the R₂O constituents within the melt may not be desirable.As the tungsten segregates, it is difficult to saturate the glass withit, and accordingly, it is difficult to get it to crystallize from theglass and form the precipitates as described herein.

It has been discovered by the inventors of the present disclosure that ahomogeneous single-phase W or Mo-containing peralkaline melt may beobtained through the use of “bound” alkalis. For purposes of thisdisclosure, “bound” alkalis are alkali elements which are bonded tooxygen ions which are bound to aluminum, boron, and/or silicon atoms,while “free” or “unbound” alkalis are alkali carbonates, nitrates, orsulfates, which are not bound to an oxygen ion already bound to silicon,boron, or aluminum, atoms. Exemplary bound alkalis may include feldspar,nepheline, borax, spodumene, other sodium or potassium feldspars,alkali-aluminum-silicates and/or other oxide compositions containing analkali and one or more aluminum and/or silicon atoms. By introducing thealkali in the bound form, the alkalis may not react with the W or Mopresent in the melt to form the dense alkali tungstate and/or alkalimolybdate liquid. Moreover, this change in batch material may allow themelting of strongly peralkaline compositions (e.g., R₂O—Al₂O₃=about 2.0mol % or more) without the formation of an alkali tungstate and/oralkali molybdate second phase. This has also allowed the melttemperature and mixing method to be varied and still produce asingle-phase homogeneous glass. It will be understood that as the alkalitungstate phase and the borosilicate glass are not immiscible, andprolonged stirring of the molten mixture may also allow mixing of thetwo phases to cast a single phase article.

Once the glass melt is cast and solidified into the glass state article,the article 10 may be annealed, heat treated or otherwise thermallyprocessed to form or modify a crystalline phase within the article 10.Accordingly, the article 10 may be transformed from the glass-state tothe glass-ceramic state. The crystalline phase of the glass-ceramicstate may take a variety of morphologies. According to various examples,the crystalline phase is formed as a plurality of precipitates withinthe heat treated region of the article 10. As such, the precipitates mayhave a generally crystalline structure. The glass-ceramic state mayinclude two or more crystalline phases.

As used herein, “a crystalline phase” refers to an inorganic materialwithin the articles of the disclosure that is a solid composed of atoms,ions or molecules arranged in a pattern that is periodic in threedimensions. Further, “a crystalline phase” as referenced in thisdisclosure, unless expressly noted otherwise, is determined to bepresent using the following method. First, powder x-ray diffraction(“XRD”) is employed to detect the presence of crystalline precipitates.Second, Raman spectroscopy (“Raman”) is employed to detect the presenceof crystalline precipitates in the event that XRD is unsuccessful (e.g.,due to size, quantity and/or chemistry of the precipitates). Optionally,transmission electron microscopy (“TEM”) is employed to visually confirmor otherwise substantiate the determination of crystalline precipitatesobtained through the XRD and/or Raman techniques. In certaincircumstances, the quantity and/or size of the precipitates may be lowenough that visual confirmation of the precipitates proves particularlydifficult. As such, the larger sample size of XRD and Raman may beadvantageous in sampling a greater quantity of material to determine thepresence of the precipitates.

The crystalline precipitates may have a generally rod-like orneedle-like morphology. The precipitates may have a longest lengthdimension of from about 1 nm to about 500 nm, or from about 1 nm toabout 400 nm, or from about 1 nm to about 300 nm, or from about 1 nm toabout 250 nm, or from about 1 nm to about 200 nm, or from about 1 nm toabout 100 nm, or from about 1 nm to about 75 nm, or from about 1 nm toabout 50 nm, or from about 5 nm to about 50 nm, or from about 1 nm toabout 25 nm, or from about 1 nm to about 20 nm, or from about 1 nm toabout 10 nm. The size of the precipitates may be measured using ElectronMicroscopy. For purposes of this disclosure, the term “ElectronMicroscopy” means visually measuring the longest length of theprecipitates first by using a scanning electron microscope, and ifunable to resolve the precipitates, next using a transmission electronmicroscope. As the crystalline precipitates may generally have arod-like or needle-like morphology, the precipitates may have a width offrom about 5 nm to about 50 nm, or from about 2 nm to about 30 nm, orfrom about 2 nm to about 10 nm, or from about 2 nm to about 7 nm. Itwill be understood that the size and/or morphology of the precipitatesmay be uniform, substantially uniform or may vary. Generally,peraluminous compositions of the article 10 may produce precipitateshaving a needle-like shape with a length of from about 100 nm to about250 nm and a width of from about 5 nm to about 30 nm. Peraluminouscompositions are compositions that have a molecular proportion ofaluminum oxide higher than the combination of sodium oxide, potassiumoxide and calcium oxide. Peralkaline compositions of the article 10 mayproduce needle-like precipitates having a length of from about 10 nm toabout 30 nm and a width of from about 2 nm to about 7 nm. Ag, Au and/orCu containing examples of the article 10 may produce rod-likeprecipitates having a length of from about 2 nm to about 20 nm and awidth, or diameter, of from about 2 nm to about 10 nm. A volume fractionof the crystalline phase in the article 10 may range from about 0.001%to about 20%, or from about 0.001% to about 15%, or from about 0.001% toabout 10%, or from about 0.001% to about 5%, or from about 0.001% toabout 1%.

The relatively small size of the precipitates may be advantageous inreducing the amount of light scattered by the precipitates leading tohigh optical clarity of the article 10 when in the glass-ceramic state.As will be explained in greater detail below, the size and/or quantityof the precipitates may be varied across the article 10 such thatdifferent portions of the article 10 may have different opticalproperties. For example, portions of the article 10 where theprecipitates are present may lead to changes in the absorbance, color,reflectance and/or transmission of light, as well as the refractiveindex as compared to portions of the article 10 where differentprecipitates (e.g., size and/or quantity) and/or no precipitates arepresent. As such, the first portion 34 and the second portion 38 mayexhibit differences in the absorbance, color, reflectance and/ortransmission of light, as well as the refractive index.

The precipitates may be composed of the oxides of tungsten and/ormolybdenum.

The crystalline phase includes an oxide, from about 0.1 mol % to about100 mol % of the crystalline phase, of at least one of: (i) W, (ii) Mo,(iii) V and an alkali metal cation, and (iv) Ti and an alkali metalcation. Without being bound by theory, it is believed that duringthermal processing (e.g., heat treating) of the article 10, tungstenand/or molybdenum cations agglomerate to form crystalline precipitatesthereby transforming the glass state into the glass-ceramic state. Themolybdenum and/or tungsten present in the precipitates may be reduced,or partially reduced. For example, the molybdenum and/or tungsten withinthe precipitates may have an oxidation state of between 0 and about +6,or from about +4 and about +6, or from about +5 and about +6. Accordingto various examples, the molybdenum and/or tungsten may have a +6oxidation state. For example, the precipitates may have the generalchemical structure of WO₃ and/or MoO₃. The precipitates may be known asnon-stoichiometric tungsten suboxides, non-stoichiometric molybdenumsuboxides, “molybdenum bronzes” and/or “tungsten bronzes.” One or moreof the above-noted alkali metals and/or dopants may be present withinthe precipitates. Tungsten and/or molybdenum bronzes are a group ofnon-stoichiometric tungsten and/or molybdenum sub-oxides that takes thegeneral chemical form of M_(x)WO₃ or M_(x)MoO₃, where M=H, Li, Na, K,Rb, Cs, Ca, Sr, Ba, Zn, Ag, Au, Cu, Sn, Cd, In, Tl, Pb, Bi, Th, La, Pr,Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and U, and where 0<x<1. Thestructures M_(x)WO₃ and M_(x)MoO₃ are considered to be a solid-statedefect structure in which holes (vacancies and/or interstices) in areduced WO₃ or MoO₃ network are randomly occupied by M atoms, which aredissociated into M⁺ cations and free electrons. Depending on theconcentration of “M,” the material properties can range from metallic tosemiconducting, thereby allowing a variety of optical absorption andelectronic properties to be tuned. It will be understood that mixedtungsten and molybdenum bronzes may also be formed. For example, mixedtungsten and molybdenum bronzes M′_(x)M″″O₃, where M′ is an alkali(e.g., Li, Na, K, Rb, Cs), 0<x<1, and M″″O₃ is a mixture of WO₃ andMoO₃.

A portion, a majority, substantially all or all of the article 10 may bethermally processed to form the precipitates. For example, the firstportion 34 and the second portion 38 may be processed differently or oneportion (e.g., the first portion 34) may not be thermally processedwhile the other portion (e.g., the second portion 38) is thermallyprocessed. Thermal processing techniques may include, but are notlimited to, a furnace (e.g., a heat treating furnace), a laser and/orother techniques of locally and/or bulk heating of the article 10. Itwill be understood that thermal processing also encompasses localizedcooling (e.g., through heat sinks and/or cold jets of gas) of regions orareas of the substrate 14 while other areas or regions of the substrate14 are heated. While undergoing thermal processing, the crystallineprecipitates internally nucleate within the article 10 in a homogenousmanner where the article 10 is thermally processed to form theglass-ceramic state. As such, in some examples, the article 10 mayinclude both glass and glass-ceramic portions. In examples where thearticle 10 is thermally processed in bulk (e.g., the whole article 10 isplaced in a furnace), the precipitates may homogenously form throughoutthe article 10. In other words, the precipitates may exist from asurface of the article 10 throughout the bulk of the article 10 (i.e.,greater than about 10 μm from the surface). In examples where thearticle 10 is thermally processed locally (e.g., via a laser), theprecipitates may only be present where the thermal processing reaches asufficient temperature (e.g., at the surface and into the bulk of thearticle 10 proximate the heat source). It will be understood that thearticle 10 may undergo more than one thermal processing to produce theprecipitates. Additionally or alternatively, thermal processing may beutilized to remove and/or alter precipitates which have already beenformed (e.g., as a result of previous thermal processing). For example,thermal processing may result in the decomposition of precipitatesand/or the alteration of their structure, size and/or chemistry. Thermalprocessing may also include contacting one or more heat sinks, infraredblocking agents and/or other items configured to speed or delay heatingand/or cooling of portions of the article 10. Such changes in theheating and/or cooling rate of the substrate 14 may affect the quantity,size and/or chemistry of the crystalline precipitates which may lead tochanges in optical properties between the first portion 34 and thesecond portion 38 as explained in greater detail below.

According to various examples, the article 10 may be polychromatic. Forpurposes of this disclosure, the term “polychromatic” means a materialwhich is capable of exhibiting different colors based on thermaltreatments applied to it. WO₃ has no absorption of NIR wavelengths andonly weak absorbance of visible wavelengths due to its wide band gap(e.g., about 2.62 eV) and lack of free carriers (e.g., electrons). Withthe insertion (termed ‘intercalation’) of dopant ions (e.g., NH₄ ⁺, Li⁺,Na⁺, K⁺, Rb⁺, Cs⁺, etc.), part of tungsten atoms in WO₃ are reduced fromW⁺⁶ to W⁺⁵, resulting in free electrons within the crystal. Theseelectrons occupy conduction bands (e.g., free electrons) and localizedstates in bandgaps (e.g., trapped electrons). As a result, the doped WO₃(tungsten bronzes) acquires the ability of blocking NIR Over a widewavelength range (e.g., λ>1100 nm) by absorbing NIR whose photon energyis lower than 0.7 eV through localized surface plasmon resonance andinsulating NIR whose photon energy is near 1.4 eV through a smallpolaron mechanism. It will be understood that the same manner of dopingand its effects are present in compositions including MoO₃ as well ascompositions with both WO₃ and MoO₃.

Conventional glass compositions which utilize Ag, Au and/or Cu rely onthe formation of nanoscale metallic precipitates to generate colors. Ag,Au and/or Cu cations can also intercalate into WO₃ and MoO₃ formingsilver, gold and/or copper tungsten bronzes and/or silver, gold and/orcopper molybdenum bronzes which may allow the article 10 exhibitpolychromatic optical properties. Surprisingly, with the addition of asmall concentration of Ag, Au and/or Cu to M_(x)WO₃ and/or M_(x)MoO₃containing articles 10, a variety of colors (e.g., red, orange, yellow,green, blue, various browns and/or combinations thereof) could beproduced by thermally processing the material at different times andtemperatures. This result was quite unexpected because post-formationoptical testing of the resultant articles 10 did not show evidence thatthe colors produced were simply summations of the optical absorptionfrom the alkali tungsten and/or molybdenum bronzes phase (e.g., blue orgreen color) and absorbance characteristic of metallic nanoparticles(e.g., metallic Ag⁰, Au⁰ and/or Cu⁰). Further analysis demonstrated thatthe color tunability was not due to the formation of ensembles ofmetallic nanoparticles that template atop a crystalline phase (e.g.,M_(x)WO₃ or M_(x)MoO₃). For example, transmission electron microscopyrevealed that the total volume fraction of the tungsten and/ormolybdenum-containing crystalline phase, the crystallite size, shape,and aspect ratio remained constant irrespective of the color. Similarly,Raman spectroscopy detected tungsten and/or molybdenum bronze phases,but not the presence of metallic nanoparticles of any shape or size. Assuch, the resultant color and polychromatic nature of the article 10does not manifest from some change in the tungsten and/ormolybdenum-containing crystallite precipitate size.

In view of the above discussion, it is believed that the origin of colortunability in these polychromatic articles 10 is due to the change inthe band gap energy of the doped tungsten and/or molybdenum oxideprecipitates, arising from the concentration of intercalated alkalications, as well as Ag, Au and/or Cu dopant metal cations, into theprecipitates to form a pure alkali, mixed alkali-metal, and/or a puremetal tungsten and/or molybdenum bronzes of varying stoichiometry.Hence, examples of the polychromatic articles 10 have a plurality ofcrystalline precipitates that include non-stoichiometric tungsten,molybdenum and/or mixed molybdenum suboxides, some or all of which areintercalated with dopant cations (e.g., transition metals such as Ag, Auand/or Cu) and/or alkali metal ions. Changes in the band gap energy ofthe precipitates are due to its stoichiometry and in-turn is largelyindependent of crystallite size. Therefore, doped M_(x)WO₃ or M_(x)MoO₃precipitates can remain the same size and/or shape, yet could providethe article 10 with many different colors depending on the dopant “M”identity and concentration “x”. Further, it is believed that the thermalprocessing time and temperature control the stoichiometry “x” andpossibly the identity of “M.” For example, at relatively lowtemperatures, blue and green colors were observed that arecharacteristic of a M_(x)WO₃ and/or M_(x)MoO₃ bronze, where M=an alkaliand 0.1<x<0.4. At temperatures above where these ‘blue bronzes’ form,colors such as yellow, red, and orange are formed, that suggest that “x”in M_(x)WO₃ is >0.4 and approaches 1 with increasing heat treatmenttime.

As such, the polychromatic nature, or color tunability, is a function ofthe concentration and identity of “M” in M_(x)WO₃ and M_(x)MoO₃ when Mis something else other than sodium (i.e., x Na), or M is a combinationof species: H, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Sn, P, S, Ti, V, Cr, Mn,Fe, Co, Ni, Cu, Ga, Se, Zr, Nb, Ru, Rh, Pd, Ag, Cd, In, Sb, Te, La, Ce,Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ta, Os, Ir, Pt, Au, Tl,Pb, Bi, and/or U. The resultant color is due to the total dopantconcentration x and also the identities of M (i.e., species withdifferent electron densities, but the same charge can produce differentoptical responses). As will be understood, some of the species listedcan only intercalate up to some x value (i.e., a narrower range of xthan 0<x<1). This may be due to the cation size and charge. For example,red, yellow and/or orange colors can be obtained from non-stoichiometrictungstate compounds containing divalent cations M′ where M′ is one ofMgO, CaO, SrO, BaO, ZnO, of the form M′_(2-X)WO₄ (where 0<x<1).

The thermal processing of the article 10 to develop the precipitatesand/or generate color and/or optical absorbance may be accomplished in asingle step or through multiple steps. For example, the generation ofcolors exhibited by the article 10 (e.g., which starts with theformation of a WO₃ and/or MoO₃ precipitates followed by the partialreduction of that crystallite with the simultaneous intercalation of adopant species (e.g., an Ag, Au and/or Cu cation into the crystal)) canbe completed in a single heat treatment after immediately after thearticle 10 is formed, or at a later point. For example, the article 10may be cast and then processed into a final form (e.g., lens blanks orother optical or aesthetic elements) and then annealed at a temperaturejust below where color is generated (e.g., intercalation of the Ag, Auand/or Cu ions into the precipitates). This annealing may start theclustering of WO₃ and/or MoO₃, and then a secondary thermal processingmay occur at an elevated temperature to allow further crystallizationand the partial reduction of the WO₃ and/or MoO₃ crystals andintercalation of Ag, Au, Cu, and/or other species to generate color.

The thermal processing of the article 10, which generates theprecipitates and/or intercalates the dopants into the precipitates, mayoccur under a variety of times and temperatures. It will be understoodthat thermal processing of the article 10 is carried out in an inertatmosphere (e.g., N₂ and/or air) unless otherwise noted. In exampleswhere the article 10 is thermally processed in a furnace, the article 10may be placed in the furnace at room temperature with a controlledramping in temperature and/or may be “plunged” into a furnace already atan elevated temperature. The thermal processing may occur at atemperature of from about 400° C. to about 1000° C., or from about 400°C. to about 700° C., or from about 450° C. to about 650° C. For example,the second thermal processing may take place at a temperature of about400° C., or about 425° C., or about 450° C., or about 475° C., or about500° C., or about 505° C., or about 510° C., or about 515° C., or about520° C., or about 525° C., or about 530° C., or about 535° C., or about540° C., or about 545° C., or about 550° C., or about 555° C., or about560° C., or about 565° C., or about 570° C., or about 575° C., or about580° C., or about 585° C., or about 590° C., or about 595° C., or aboutor about 600° C., or about 605° C., or about 610° C., or about 615° C.,or about 620° C., or about 625° C., or about 630° C., or about 635° C.,or about 640° C., or about 645° C., or about 650° C., or about 655° C.,or about 660° C., or about 665° C., or about 670° C., or about 675° C.,or about 680° C., or about 685° C., or about 690° C., or about 695° C.,or about 700° C. It will also be understood that any and all values andranges between these specified thermal processing temperatures arecontemplated for article 10.

The thermal processing may be carried out for a time period of fromabout 1 second to about 24 hours, or from about 5 minutes to about 500minutes, or from about 5 minutes to about 300 minutes. For example, thethermal processing may be carried out for about 1 second, or about 30seconds, or about 45 seconds, or about 1 minute, or about 2 minutes, orabout 5 minutes, or about 10 minutes, or about 15 minutes, or about 20minutes, or about 25 minutes, or about 30 minutes, or about 35 minutes,or about 40 minutes, or about 45 minutes, or about 50 minutes, or about55 minutes, or about 60 minutes, or about 65 minutes, or about 70minutes, or about 75 minutes, or about 80 minutes, or about 85 minutes,or about 90 minutes, or about 95 minutes, or about 100 minutes, or about105 minutes, or about 110 minutes, or about 115 minutes, or about 120minutes, or about 125 minutes, or about 130 minutes, or about 135minutes, or about 140 minutes, or about 145 minutes, or about 150minutes, or about 155 minutes, or about 160 minutes, or about 165minutes, or about 170 minutes, or about 175 minutes, or about 180minutes, or about 185 minutes, or about 190 minutes, or about 195minutes, or about 200 minutes, or about 205 minutes, or about 210minutes or about 215 minutes, or about 220 minutes, or about 225minutes, or about 230 minutes, or about 235 minutes, or about 240minutes, or about 245 minutes, or about 250 minutes, or about 255minutes, or about 300 minutes. It will be understood that thermalprocessing may be carried out for significantly longer times upwards ofabout 6 hours or more, 7 hours or more, 8 hours or more, 9 hours ormore, 10 hours or more, 11 hours or more, 12 hours or more, 13 hours ormore, 14 hours or more or 15 hours or more. It will be understood thatbased on the heat and/or cooling configuration of the article 10 andsubstrate 14, the first portion 34 and the second portion 38 may each beheld at different temperatures for different amount of times. It willalso be understood that any and all values and ranges between thesespecified thermal processing durations are contemplated for article 10.

In some examples, the article 10 may then be cooled to a lowertemperature at a rate of about 0.1° C. per minute to about 100° C. perminute, or about 0.1° C. per minute to about 50° C. per minute, or fromabout 0.1° C. per minute to about 10° C. per minute. For example,article 10 may be cooled at a lower temperature at a rate of about 0.1°C. per minute, or about 0.5° C. per minute, or about 1° C. per minute,or about 1.5° C. per minute, or about 2° C. per minute, or about 3° C.per minute, or about 4° C. per minute, or about 5° C. per minute, orabout 6° C. per minute, or about 7° C. per minute, or about 8° C. perminute, or about 9° C. per minute, or about 10° C. per minute, or about20° C. per minute, or about 30° C. per minute, or about 40° C. perminute, or about 50° C. per minute, or about 60° C. per minute, or about70° C. per minute, or about 80° C. per minute, or about 90° C. perminute, or about 100° C. per minute. It will be understood thatdifferent portions of the article 10, such as first portion 34 andsecond portion 38, may be cooled at different rates as explained ingreater detail below. For example, the first portion 34 and the secondportion 38 may be cooled at different rates to produce different opticaland/or mechanical properties across the substrate 14. It will also beunderstood that any and all values and ranges between these specifiedthermal processing cooling rates are contemplated for article 10.

The lower temperature may be from about room temperature (e.g., 23° C.)to about 500° C., or from about room temperature to about 400° C., orfrom about 100° C. to about 400° C. For example, the lower temperaturemay be about 23° C., about 50° C., about 75° C., about 100° C., about125° C., about 150° C., about 175° C., about 200° C., about 225° C.,about 250° C., about 275° C., about 300° C., about 325° C., about 350°C., about 375° C., about 400° C., or about 425° C., or about 450° C., orabout 470° C., or about 500° C. It will be understood that the article10 may undergo a multistage thermal processing using one or more of theabove noted time and temperatures. It will also be understood that anyand all values and ranges between these specified thermal processinglower temperatures are contemplated for article 10.

As explained above, additionally or alternatively to the use of afurnace, the article 10 may be thermally processed through the use oflaser and/or other localized heat source. One example of a localizedheat source may include a preheated heat sink which is placed onto thearticle 10 and/or substrate 14 which to locally heat one or more of thefirst portion 34 and the second portion 38. In will be understood thatthe substrate 14 may be at room temperature or preheated prior to theplacement of the preheated heat sink. Such an example may beadvantageous in producing a localized color or polychromatic effect. Thelaser and/or localized heat source may supply sufficient thermal energyto create the precipitates and/or intercalate one or more of Ag, Auand/or Cu into the precipitates to generate localized color. The laserand/or other heat source may be rastered or guided across the article 10to preferentially create color and/or varied optical properties acrossthe article 10. The intensity and/or speed of the laser and/or localizedheat source may be adjusted as it is moved across the article 10 suchthat various portions of the article 10 exhibit different colors orabsorbance. Such features may be advantageous in creating indicia,symbols, text, numbers and/or pictures in the article 10. Further, sucha feature may be advantageous in creating a gradient tint.

As explained above, depending on the composition of the article 10 andthe thermal processing it undergoes, the article 10 may exhibit avariety of colors. Specifically, the article 10 may exhibit thefollowing colors: blue, green, brown, amber, yellow, orange, red,oxblood red, shades of neutral gray and bronze-brown colors and/orcombinations thereof. It will be understood that any of these colorsand/or color combinations may be generated in bulk across the article 10and/or in localized portions of the article 10 (e.g., first portion 34and second portion 38) as explained above. The color of the article 10may be expressed in terms of a three-dimensional L*a*b* color spacewhere L** is lightness and a* and b* for the color opponents green-redand blue-yellow, respectively. Additionally or alternatively, the colorof the article 10 may also be expressed in values of X and Y where Y isluminance and X is a mix (e.g., a linear combination) of cone responsecurves chosen to be nonnegative. Unless otherwise specified the L*, a*,b* and X, Y color coordinates, with specular component included, arecollected under D65-10 illumination with an X-Rite colorimeter intransmittance mode on polished 0.5 mm thick flats cut from rolled sheetafter heat treatment. In other words, the color coordinates aretransmitted color coordinates. The article 10 may exhibit an L* value offrom about 6 to about 90, or from about 6 to about 85, or from about 4to about 86, or from about 14 to about 90, or from about 21 to about 88,or from about 4.5 to about 81, or from about 39 to about 90, or fromabout 8 to about 90, or from about 15 to about 91, or from about 28 toabout 92, or from about 16 to about 81, or from about 49 to about 89, orfrom about 41 to about 96 or from about 15.6 to about 96. The article 10may exhibit an a* value from about −18.6 to about 49, or from about −13to about 41, or from about −9 to about 38, or from about −14 to about31, or from about −11 to about 36, or from about −12 to about 29 or fromabout −12 to about 26. The article 10 may exhibit a b* value of fromabout −7.8 to about 53.5, or from about −2 to about 63, or from about 2to about 70, or from about 6 to about 70, or from about 1 to about 68,or from about 1 to about 65, or from about 4 to about 49, or from about1 to about 37, or from about 4 to about 24 or from about 5 to about 30.The article 10 may exhibit an X value of from about 0.24 to about 0.65,or from about 0.31 to about 0.66, or from about 0.27 to about 0.62, orfrom about 0.29 to about 0.66, or from about 0.30 to about 0.65, or fromabout 0.29 to about 0.60, or from about 0.31 to about 0.57 or from about0.3 to about 0.48. The article 10 may exhibit a Y value of from about0.32 to about 0.43, or from about 0.34 to about 0.40, or from about 0.33to about 0.43 or from about 0.35 to about 0.38. It will be understoodthat all values and ranges between the above-noted ranges and values arecontemplated for L*, a*, b*, X and Y. Further, it will be understoodthat any of the L*, a*, b*, X and Y values may be used in conjunctionwith any of the other L*, a*, b*, X and Y values.

The article 10 may exhibit an absorbance over certain wavelength bandsof electromagnetic radiation. It will be understood that as theformation of the crystalline precipitates increases absorbance of thesubstrate 14, any and all manners described above in connection withgenerating color may also equally alter absorbance of the substrate 14.The absorbance may be expressed in terms of optical density permillimeter (OD/mm). As understood by those in the art, optical densityis the log of the ratio of light intensity exiting the article 10 tolight intensity entering the article 10. Absorbance data may becollected using a UV/VIS/NIR spectrophotometer in conformance with themeasurement rules according to ISO 15368.

Over a wavelength range of from about 280 nm to about 380 nm, the firstportion 34 and/or the second portion 38, of the article 10 may have anabsorbance of 0.5 OD/mm to about 20 OD/mm, or from about 0.5 OD/mm toabout 10 OD/mm, or from about 0.6 OD/mm to about 8 OD/mm, or from about1 OD/mm to about 8 OD/mm, or from about 4 OD/mm to about 8 OD/mm. Forexample, the article 10 may have an absorbance over a wavelength of fromabout 280 nm to about 380 nm of about 0.5 OD/mm, or about 1.0 OD/mm, orabout 1.5 OD/mm, or about 2.0 OD/mm, or about 2.5 OD/mm, or about 3.0OD/mm, or about 3.5 OD/mm, or about 4.0 OD/mm, or about 4.5 OD/mm, orabout 5.0 OD/mm, or about 5.5 OD/mm, or about 6.0 OD/mm, or about 6.5OD/mm, or about 7.0 OD/mm, or about 7.5 OD/mm, or about 8.0 OD/mm, orabout 8.5 OD/mm, or about 9.0 OD/mm, or about 9.5 OD/mm, or about 10.0OD/mm or greater. It will be understood that any and all values andranges between the values listed above are contemplated.

Over a wavelength range of from about 380 nm to about 400 nm, the firstportion 34 and/or the second portion 38 of the article 10 may have anabsorbance of about 0.2 OD/mm to about 20 OD/mm, or about 0.2 OD/mm toabout 10 OD/mm, or from about 0.2 OD/mm to about 8 OD/mm, or from about1.2 OD/mm to about 8 OD/mm, or from about 1.8 OD/mm to about 7.5 OD/mm.For example, the article 10 may have an absorbance over a wavelength offrom about 380 nm to about 400 nm of about 0.5 OD/mm, or about 1.0OD/mm, or about 1.5 OD/mm, or about 2.0 OD/mm, or about 2.5 OD/mm, orabout 3.0 OD/mm, or about 3.5 OD/mm, or about 4.0 OD/mm, or about 4.5OD/mm, or about 5.0 OD/mm, or about 5.5 OD/mm, or about 6.0 OD/mm, orabout 6.5 OD/mm, or about 7.0 OD/mm, or about 7.5 OD/mm, or about 8.0OD/mm, or about 8.5 OD/mm, or about 9.0 OD/mm, or about 9.5 OD/mm, orabout 10.0 OD/mm or greater. It will be understood that any and allvalues and ranges between the values listed above are contemplated.

Over a wavelength range of from about 400 nm to about 700 nm, the firstportion 34 and/or the second portion 38 of the article 10 may have anabsorbance of 0.1 OD/mm to about 6 OD/mm, or from about 0.1 OD/mm toabout 4.4 OD/mm, or from about 0.6 OD/mm to about 4.2 OD/mm. Forexample, the article 10 may have an absorbance over a wavelength of fromabout 400 nm to about 700 nm of about 0.5 OD/mm, or about 1.0 OD/mm, orabout 1.5 OD/mm, or about 2.0 OD/mm, or about 2.5 OD/mm, or about 3.0OD/mm, or about 3.5 OD/mm, or about 4.0 OD/mm, or about 4.5 OD/mm, orabout 5.0 OD/mm, or about 5.5 OD/mm or about 6.0 OD/mm. It will beunderstood that any and all values and ranges between the values listedabove are contemplated.

Over a wavelength range of from about 700 nm to about 2000 nm, the firstportion 34 and/or the second portion 38 of the article 10 may have anabsorbance of 0.1 OD/mm to about 5.7 OD/mm, or from about 0.1 OD/mm toabout 5.8 OD/mm or from about 0.1 OD/mm to about 5.2 OD/mm. For example,over a wavelength range of from about 700 nm to about 2000 nm, thearticle 10 may have an absorbance of about 0.2 OD/mm, or about 0.4OD/mm, or about 0.6 OD/mm, or about 0.8 OD/mm, or about 1.0 OD/mm, orabout 1.2 OD/mm, or about 1.4 OD/mm, or about 1.6 OD/mm, or about 1.8OD/mm, or about 2.0 OD/mm, or about 2.2 OD/mm, or about 2.4 OD/mm, orabout 2.6 OD/mm, or about 2.8 OD/mm, or about 3.0 OD/mm, or about 3.2OD/mm, or about 3.4 OD/mm, or about 3.6 OD/mm, or about 3.8 OD/mm, orabout 4.0 OD/mm, or about 4.2 OD/mm, or about 4.4 OD/mm, or about 4.6OD/mm, or about 4.8 OD/mm, or about, or about 5.0 OD/mm, or about 5.2OD/mm, or about 5.4 OD/mm, or about 5.6 OD/mm or about 5.8 OD/mm. Itwill be understood that any and all values and ranges between the valueslisted above are contemplated.

Over a wavelength range of from about 400 nm to about 1500 nm, thearticle 10 may have a difference in absorbance between the first portion34 and the second portion 38 of about 0.04 OD/mm or greater, or about0.05 OD/mm or greater, or about 0.10 OD/mm or greater, or about 0.15OD/mm or greater, or about 0.20 OD/mm or greater, or about 0.25 OD/mm orgreater, or about 0.30 OD/mm or greater, or about 0.35 OD/mm or greater,or about 0.40 OD/mm or greater, or about 0.45 OD/mm or greater, or about0.49 OD/mm or greater, or about 0.50 OD/mm or greater, or about 0.55OD/mm or greater, or about 0.60 OD/mm or greater, or about 0.65 OD/mm orgreater, or about 0.60 OD/mm or greater, or any and all absorbancevalues between the given values. For example, the difference inabsorbance between the first portion 34 and the second portion 38 mayrange from about 0.04 OD/mm to about 0.70 OD/mm, or from about 0.04OD/mm to about 0.60 OD/mm, or from about 0.04 OD/mm to about 0.50 OD/mm,or from about 0.04 OD/mm to about 0.49 OD/mm, or from about 0.04 OD/mmto about 0.40 OD/mm, or from about 0.04 OD/mm to about 0.30 OD/mm, orfrom about 0.04 OD/mm to about 0.20 OD/mm, or from about 0.04 OD/mm toabout 0.10 OD/mm.

Over a wavelength range of from about 400 nm to about 750 nm, thearticle 10 may have a difference in absorbance between the first portion34 and the second portion 38 of about 0.04 OD/mm or greater, or about0.05 OD/mm or greater, or about 0.10 OD/mm or greater, or about 0.5OD/mm or greater, or about 1 OD/mm or greater, or about 5 OD/mm orgreater, or about 10 OD/mm or greater, or about 15 OD/mm or greater, orabout 20 OD/mm or greater, or about 25 OD/mm or greater, or about 30OD/mm or greater, or about 35 OD/mm or greater, or about 40 OD/mm orgreater, or about 45 OD/mm or greater, or about 49 OD/mm or greater, orabout 50 OD/mm or greater, or about 55 OD/mm or greater, or about 60OD/mm or greater, or about 65 OD/mm or greater, or about 60 OD/mm orgreater, or any and all absorbance values between the given values. Forexample, the difference in absorbance between the first portion 34 andsecond portion 38 may range from about 0.04 OD/mm to about 70 OD/mm, orfrom about 0.04 OD/mm to about 60 OD/mm, or from about 0.04 OD/mm toabout 50 OD/mm, or from about 0.04 OD/mm to about 49 OD/mm, or fromabout 0.04 OD/mm to about 40 OD/mm, or from about 0.04 OD/mm to about 30OD/mm, or from about 0.04 OD/mm to about 20 OD/mm, or from about 0.04OD/mm to about 10 OD/mm.

The article 10 may exhibit a “Contrast Ratio” between the first portion34 and second portion 38. The Contrast Ratio is defined as the averageabsorbance of the second portion 38 over a given wavelength rangedivided by the average absorbance of the first portion 34 over the samewavelength range. Over a wavelength range of from about 400 nm to about750 nm (e.g., visible light), the Contrast Ratio between the firstportion 34 and the second portion 38 may be about 1, or about 1.4, orabout 2, or about 5, or about 10, or about 20, or about 30, or about 40,or about 50, or about 60, or about 70, or about 80, or about 90, orabout 100, or about 110, or about 120, or about 130, or about 140, orabout 150, or about 160, or about 165, or about 170, or about 180, orabout 190 or about 200, or any and all values and ranges between thegiven values. For example, the Contrast Ratio between the first portion34 and the second portion 38 or a wavelength range of from about 400 nmto about 750 nm may be from about 1.4 to about 200, or from about 1.4 toabout 190, or from about 1.4 to about 165, or from about 1.4 to about120, or from about 1.4 to about 90, or from about 1.4 to about 50, orfrom about 1.4 to about 20, or from about 1.4 to about 10.

Over a wavelength range of from about 750 nm to about 1500 nm (e.g.,visible light), the Contrast Ratio between the first portion 34 and thesecond portion 38 may be about 1, or about 1.5, or about 2, or about2.5, or about 3, or about 3.5, or about 4, or about 4.5, or about 5, orabout 5.5, or about 6, or about 6.5, or about 7, or about 7.5, or about8, or about 8.5, or about 9, or about 9.5, or about 10, or about 10.5,or about 11, or about 11.5, or about 12, or about 12.5, or about 13, orabout 13.5, or about 14, or about 14.5, or about 15, or about 15.5, orabout 16, or about 16.5, or about 17, or about 17.5, or about 18, orabout 18.5, or about 19, or about 19.5, or about 20, or about 20.5, orany and all values and ranges between the given values. For example, theContrast Ratio between the first portion 34 and the second portion 38over a wavelength range of from about 750 nm to about 1500 nm may befrom about 1.5 to about 20, or from about 1.5 to about 18, or from about1.5 to about 14, or from about 1.5 to about 10, or from about 1.5 toabout 8, or from about 1.5 to about 5, or from about 1.5 to about 3.

The article 10 may exhibit differing transmittances over differentwavelength bands of electromagnetic radiation. The transmittance may beexpressed in a percent transmittance. Transmittance data may becollected using a UV/VIS/NIR spectrophotometer on a sample having a 0.5mm thickness in conformance with the measurement rules according to ISO15368. Over a wavelength range of from about 280 nm to about 380 nm, thearticle 10 may have a transmittance of 0% to about 50%, or from about0.01 to about 30%, or from about 0.01% to about 0.91%. For example, thearticle 10 may have a transmittance over a wavelength of from about 280nm to about 380 nm of about 0.5%, or about 5%, or about 10%, or about15%, or about 20%, or about 25%, or about 30%, or about 35%, or about40% or about 45%. It will be understood that any and all values andranges between the values listed above are contemplated.

The article 10 may have a transmittance over a wavelength range of fromabout 380 nm to about 400 nm of 0% to about 86%, or from about 0.8% toabout 86%, or from about 0% to about 25% or from about 0.02% to about13%. For example, the article 10 may have a transmittance over awavelength of from about 380 nm to about 400 nm of about 1%, or about5%, or about 10%, or about 15%, or about 20%, or about 25%, or about30%, or about 35%, or about 40%, or about 45%, or about 50%, or about55%, or about 60%, or about 65%, or about 70%, or about 75% or about80%. It will be understood that any and all values and ranges betweenthe values listed above are contemplated. Transmittance data may becollected using a UV/VIS/NIR spectrophotometer on a sample having a 0.5mm thickness in conformance with the measurement rules according to ISO15368.

The article 10 may have a transmittance over a wavelength range of fromabout 400 nm to about 700 nm of about 0% to about 95%, or from about 0%to about 88%, or from about 0% to about 82%, or from about 0% to about70%, or from about 0% to about 60%, or from about 0% to about 50%, orfrom about 0% to about 40%, or from about 0% to about 30%, or from about0% to about 20%, or from about 0% to about 10%, or from about 5% toabout 50%, or from about 10% to about 70%. It will be understood thatany and all values and ranges between the values listed above arecontemplated. Transmittance data may be collected using a UV/Visspectrophotometer on a sample having a 0.5 mm thickness in conformancewith the measurement rules according to ISO 15368.

Over a wavelength range of from about 400 nm to about 700 nm, thearticle 10 may have a transmittance of about 0% to about 90%, or fromabout 0% to about 80%, or from about 0% to about 70%, or from about 0%to about 60%, or from about 0% to about 50%, or from about 0% to about40%, or from about 0% to about 30%, or from about 0% to about 20% orfrom about 0% to about 10%. For example, the article 10 may have atransmittance over a wavelength range from about 400 nm to about 700 nmof about 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, or 90%. It will be understood that any and allvalues and ranges between the values listed above are contemplated.Transmittance data may be collected using a UV/Vis spectrophotometer ona sample having a 0.5 mm thickness in conformance with the measurementrules according to ISO 15368.

The article 10 may exhibit a scattering of from about 0.1% to about 25%,or from about 0.1% to about 15%, or from about 0.1% to about 10%, allover a wavelength band of about 400 nm to about 700 nm at a thickness of1 mm. For example, the article 10 may exhibit a scattering of about 25%or less, about 24% or less, about 23% or less, about 22% or less, about21% or less, about 20% or less, about 19% or less, about 18% or less,about 17% or less, about 16% or less, about 15% or less, about 14% orless, about 13% or less, about 12% or less, about 11% or less, about 10%or less, about 9% or less, about 8% or less, about 7% or less, about 6%or less, about 5% or less, about 4% or less, about 3% or less, about 2%or less or about 1% or less. It will be understood that any and allvalues and ranges between the scattering values listed above arecontemplated. Scattering data is collected in conformance with ISO 13696(2002) Optics and Optical Instruments—Test methods for radiationscattered by optical components.

According to various examples, the article 10 may exhibit a reflectivemirror-like surface.

For example, one or more of primary surfaces 18 and 22 may exhibit areflection greater than typical Fresnel reflections produced by glassesand/or glass-ceramics. In such examples, the article 10 may undergo areflection treatment to produce a plurality of metallic particlesproximate one of the surfaces 18, 22. It will be understood that thereflection treatment may be performed at the same time as the thermalprocessing (i.e., as described in greater detail below) and/or at adifferent time (e.g., before and/or after the thermal processing). Thearticle 10, in such examples, may be composed of Ag containingcompositions (e.g., Ag+W, Ag+Mo+W, Ag+Au+W, or Ag+Au+Mo+W). During thereflection treatment, the article 10 may be exposed to temperatures offrom about 400° C. to about 700° C., or from about 500° C. to about 600°C. For example, the article 10 may be exposed to a temperature of about400° C., or about 425° C., or about 450° C., or about 475° C., or about500° C., or about 525° C., or about 550° C., or about 575° C., or about600° C., or about 625° C., or about 650° C., or about 675° C. or about700° C. The reflection treatment may be carried out on the article 10from about 0.5 minutes to about 360 minutes. The reflection treatmentmay be carried out in a reducing atmosphere such that the metallicprecipitates are formed. According to various examples, the atmospherearound the article 10 during the reflection treatment may contain H₂.For example, the atmosphere may have a partial pressure of H₂ of fromabout 0.5%, 1.0%, 1.5%, 2.0%, 2.5% or greater. Additionally oralternatively, the article 10 may be exposed to a gas-oxygen flame,where the gas/oxygen ratio is adjusted such that there is not completecombustion (i.e., to form a reducing atmosphere). It will be understoodthat reflection treatment (e.g., being done in a controlled oxidizing orreducing atmosphere) may be utilized to further alter the bulk orsurface composition of the article 10 and in-turn modify the opticalabsorption of the article 10.

The reflection treatment, under reducing atmospheres, causes Ag¹⁺cations in the article 10 to be reduced to form metallic silverprecipitates within the body of the article 10 that are sufficientlylarge (e.g., >50 nm) to scatter visible wavelengths of light (e.g.,about 400 nm to about 700 nm). By controlling the time and temperatureof the reflection treatment, Ag metal particles can be controllablyprecipitated proximate surfaces of the article 10. For example, theplurality of Ag metal particles may be present within the first fewmicrons (e.g., 0.1-20 μm) of the primary surfaces 18, 22. In yet otherexamples, the metal particles may be distributed throughout the entirethickness of the article 10 (e.g., in examples where the article 10 issufficiently thin). In examples where only a small fraction of the Agcations within the first few microns of the surface of the article 10are reduced to form metal Ag particles, the article 10 can act as apartial or broadband reflector at visible wavelengths. Thus, thereflected color of the article 10 can be changed if it only reflectscertain visible wavelengths. If a sufficient quantity of metallic silverparticles are formed, the article 10 may be tuned to uniformly reflectall visible wavelengths (i.e., acting as a broadband mirror). As thetime at a given temperature of the reflection treatment is increased,the more numerous the Ag metal particles are and the deeper within thearticle 10 the Ag particles form. If the reflection treatment isconducted for sufficient time and temperature, metallic Ag particles canbe precipitated throughout the entire thickness of the article 10,rendering it highly opaque.

It will be understood that other reflection treatments may be performed.For example, partially reflective surfaces can be formed by depositing(e.g., painting, applying, placing) an organic compound such as a slurryof powdered graphite or clay impregnated with an organic (e.g., sugar,corn starch, or graphite) onto the surface of the article 10 and firingit in ambient air. This enables localized reduction of the silver ionsin the article 10 by the organic agent. With such treatments, patternsof varying color and reflectivity can be produced.

The article 10 may have a reflectance over a wavelength band of fromabout 360 nm to about 760 nm prior to the reflection treatment of about10% or less, or about 9% or less, or about 8% or less, or about 7% orless, about 6% or less, about 5% or less, about 4% or less, about 3% orless, about 2% or less or about 1% or less. Once the reflectiontreatment is complete, the article 10 may have an average reflectanceover a wavelength band of from about 400 nm to about 700 nm of about 1%or greater, about 2% or greater, or about 3% or greater, or about 4% orgreater, about 5% or greater, about 6% or greater, about 7% or greater,about 8% or greater, about 9% or greater, about 10% or greater, about11% or greater, about 12% or greater, about 13% or greater, about 14% orgreater, about 15% or greater, about 16% or greater, about 17% orgreater, about 18% or greater, about 20% or greater, about 21% orgreater, about 22% or greater, about 23% or greater, about 24% orgreater or about 25% or greater. Reflected color measurements arecollected with an X-Rite colorimeter under D65-10 illuminationconditions in reflection mode.

Use of the reflection treatment may produce partially or highlyreflective coatings inside of the article 10 before and/or after theformation of the precipitates through the thermal processing. In otherwords, the article 10 may be made reflective in either the glass orglass-ceramic states. Such a feature may be advantageous in enabling thetotal extinction of the article 10 to be further modified by varying theconcentration of reduced metal particles and the concentration andstoichiometry of the absorptive precipitates. Formation of the metalparticles may be advantageous in producing a partially or broadbandreflective coating which is resistant to scratching, acids and basesbecause the reflective metal particles are formed within the first fewmicrons of the surface of the article 10, and not exclusively at thematerial's surface like many reflective coatings that are deposited byvapor deposition or wet chemical methods.

Referring now to FIG. 2, depicted is a method 50 of forming the article10. Without being bound by theory, the tungsten and molybdenum glasscrystalline precipitates develop the optical absorbance of the article10 in a fundamentally different mechanism than conventional glasses(i.e., which use tinted and/or dyed interlayers) or glass ceramics.Accordingly, adjusting process steps related to heating and coolingduring the thermal processing of the article 10 enables the tuneabilityof color in addition to the optical density, or tinting, to be readilymodulated by making simple alterations to process steps related tocooling.

The method 50 may begin with a step 54 of forming the substrate 14having a substantially homogenous bulk composition. As explained above,the substrate 14 may being in a glass-state which is free of thecrystalline precipitates. The glass substrate 14 includes the firstportion 34 and the second portion 38 which may be thermally treated inthe same or different manners as explained in greater detail below. Theglass-state substrate 14 may have may have any of the above-notedcompositions outlined with the article 10. It will be understood that,depending on the composition of the article 10, the substrate 14 mayonly briefly be in the glass-state and free of the crystallineprecipitates just after formation but that such a circumstance notbeyond the teachings provided herein.

Next, a step 58 of variably crystallizing at least one of the firstportion 34 and the second portion 38 of the substrate 14 to form theplurality of crystalline precipitates within the at least one of thefirst portion 34 and the second portions 38 is performed. The variablecrystallization of the first portion 34 and/or the second portion 38 maybe performed in a variety of manners. It will be understood that thetimes, temperatures, heating rates and cooling rates highlighted abovein connection with the thermal processing may be achieved through theexamples provided below. Further, although the different examples mayhighlight one of the first portion 34 and the second portion 38 in itsdescription, it will be understood that use of the other portion doesnot depart from the teachings provided herein.

In a first example of the variable crystallization, variablecrystallization may be performed by thermally processing the firstportion 34 and the second portion 38 of the substrate 14 at differenttemperatures. For example, the first portion 34 may be exposed and/orheated to a temperature which is lower than a temperature the secondportion 38 is exposed and/or heated to. The temperature the secondportion 38 is exposed to may be sufficiently high to generate theformation of the crystalline precipitates while the temperature thefirst portion 34 is exposed to may not be sufficiently high to form theprecipitates. In practice, such a thermal gradient or difference intemperatures between the first portion 34 and second portion 38 may beachieved in a variety of manners. In some examples, a heat sink may beplaced on the first portion 34 of the substrate 14 prior to thermalprocessing which may function to keep the temperature of the firstportion 34 from reaching a temperature in which the crystallineprecipitates form as highlighted above. Additionally or alternatively,thermally processing the first portion 34 and the second portion 38 maybe performed by selectively heating the first portion 34 or the secondportion 38 in a gradient furnace or by localized heating (e.g., throughlaser, infrared lamp, heat gun, hot item, etc.). In anotherimplementation of the first example, a preheated heat sink may be placedon the second portion 38, but not the first portion 34, such that thesecond portion 38 is selectively crystallized by thermally processingthe first portion 34 and the second portion 38 of the substrate 14 atdifferent temperatures (i.e., with the first portion 34 being at roomtemperature or another elevated temperature different than the heatsink).

In a second example of the variable crystallization, variablycrystallizing the first portion 34 and the second portion 38 may beperformed by thermally processing the first portion 34 and the secondportion 38 of the substrate 14 at the same temperature and cooling thefirst portion 34 and the second portion 38 at different cooling rates.Cooling the first portion 34 and the second portion 38 at differentrates may be performed in a variety of manners. For example, a heat sinkmay be placed on the second portion 38 of the substrate 14 during thethermal processing such that the heat sink is the same temperature asthe second portion 38. Once removed from the heat, the first portion 34without the heat sink will tend to cool faster (i.e., drop below thecrystallization temperature quicker thereby growing fewer and/or smallercrystalline precipitates) while the second portion 38 with the heat sinkwill cool slower due to the added thermal mass of the heat sink (i.e.,growing more and/or larger crystalline precipitates and/or crystallineprecipitates of different chemistries or structures). Additionally oralternatively, one or more of the first portion 34 and the secondportion 38 may be covered with an infrared shield. The infrared shieldmay be a film, coating, foil, or other structure that may be removablyplaced on or above one or more of the first portion 34 and the secondportion 38 of the substrate 14. The infrared shield may be composed of ametal (e.g., aluminum, iron, etc.) or other material configured toreflect infrared wavelength ranges of light emitted from the substrate14. Use of such an infrared shield may be advantageous in reflectinginfrared light emitted from the substrate 14 back into the substrate 14such that the cooling rate of one or more of the first portion 34 andthe second portion 38 may be slowed (i.e., due to the reabsorption ofthe infrared radiation). It will be understood that different infraredshields with different reflection/absorption characteristics may be usedon the first portion 34 and the second portion 38 such that bothportions (first portion 34 and second portion 38) include an infraredshield, but that the cooling rates of the first portion 34 and thesecond portion 38 may still be different. Through the addition of theinfrared shield and/or the heat sink and the depression of the coolingrate, the time the substrate 14 spends at an elevated temperature isincreased such that the more crystallization occurs (i.e., having agreater effect on optical properties). For example, the first portion 34and the second portion 38 of the substrate 14 may be subjected to atemperature greater than about 400° C. for different times due to theuse of the heat sink and/or the infrared shield. It will be understoodthat the heat sink and/or infrared shield may be utilized in gradienttemperature furnaces or other circumstances where non-uniform heating ofthe first portion 34 and the second portion 38 occurs such that thesubstrate 14 need not be thermally processed at the same temperature inorder to allow cooling the first portion 34 and the second portion 38 atdifferent cooling rates.

In a third example, variably crystallizing the first portion 34 and thesecond portion 38 may include increasing the temperature of the firstportion 34 and the second portion 38 at different heating rates. Forexample, a heat sink may be placed on the first portion 34 at ambienttemperature prior to the substrate 14 being placed within a furnace orother heating source. As the furnace heats to the crystallizationtemperature, the added thermal mass of the heat sink slows the heatingrate of the first portion 34 of the substrate 14. As such, the firstportion 34 may be heated at a slower rate than the second portion 38. Asthe first portion 34 with the heat sink is heated at a slower rate thanthe second portion 38 which is free of the heat sink, the time the firstportion 34 spends at the crystallization temperature may be less thanthe second portion 38 leading to selective crystallization of the secondportion 38 and increased optical density.

In a fourth example, the second portion 38 of the substrate 14 may havea preheated heat sink applied thereto in order to variably crystallizethe substrate 14. The substrate 14 may be at room temperature or may beat an elevated temperature. The heat sink may be at a temperature abovethe crystallization temperature of the substrate 14 such that the areaof the second portion 38 in contact with the preheated heat sink isselectively crystallized and changes in optical properties relative tothe first portion 34 such that the substrate 14 is variablycrystallized.

It will be understood that, although explained concisely for clarity, avariety of manners exist to accomplish the first, second, third andfourth examples of variable crystallization and that such manners may beused without departing from the teachings provided herein. For example,varied cooling or heating across the substrate 14 can be induced throughthe use of air jets or burners, or molds that have an induced thermalgradient.

By making use of the above-noted examples, the first portion 34 andsecond portion 38 may be variably crystallized by thermally processingthe first portion 34 and the second portion 38 of the substrate 14 atone or more of (a) different temperatures (i.e., examples one andthree), (b) different heating rates (i.e., example three) and (c)different thermal hold times (i.e., examples two and three). Ashighlighted above, crystallization of the substrate 14 may result in achange of the optical properties of the substrate 14 and thereforevariable crystallization of the substrate 14 may result in the selectiveformation of these optical properties. For example, the variablecrystallizing of the at least one of the first portion 34 and the secondportion 38 may result in at least one of: (a) a difference in absorbancebetween the first portion 34 and the second portion 38 of about 0.03OD/mm to about 49 OD/mm over a wavelength range of from about 400 nm toabout 750 nm, and (b) a difference in absorbance between the firstportion 34 and the second portion 38 of about 0.03 OD/mm to about 0.69OD/mm over a wavelength range of from about 750 nm to about 1500 nm.Further, the variable crystallization may generate a plurality ofcrystalline precipitates in at least one of the first portion 34 and thesecond portion 38 of the substrate 14 such that (i) a difference inabsorbance exists between the first portion 34 and the second portion 38of about 0.04 OD/mm to about 49 OD/mm over a wavelength range of fromabout 400 nm to about 750 nm and (ii) a Contrast Ratio between the firstportion 34 and the second portion 38 is from about 1.4 to about 165 overa wavelength range of from about 400 nm to about 750 nm.

Various examples of the present disclosure may offer a variety ofproperties and advantages. It will be understood that although certainproperties and advantages may be disclosed in connection with certaincompositions, various properties and advantages disclosed may equally beapplicable to other compositions.

First, use of the present disclosure allows for a simple low-cost methodof patterning the substrate 14 and portions designated to becrystallized (e.g., first portion 34 and second portion 38) only need tobe masked with foil, metal, or insulation. Further, the disclosed method50 works both in passive and active modes since the first portion 34and/or the second portion 38 can either be insulated or heated topattern. Local heat sources like burners, torches, lasers, heat lamps,or hot filaments can be used to pattern.

Second, gradient tint and color, clear apertures, patterning fordecoration, and text can be produced within substrate 14 without theneed for ultraviolet exposure through a mask as required by conventionalphoto-sensitive glasses. Such a feature may be advantageous in enablinga low-cost and aesthetically pleasing substrate 14. Further, forautomotive related examples, gradient tint may be developed in thesubstrate 14 which could replace expensive graded polyvinyl butyralinterlayers and also ink/frit boarders.

Third, the compositions of the article 10 and substrate 14 allow theproduction of glazing for automotive and architecture, housings forconsumer electronic devices, and ophthalmic lenses with gradient tint,gradient color, patterning, and or indicia (e.g., text, pictures etc.)that has been ‘developed’ within the material (i.e., not applied byetching, deposition of a pigment, or otherwise).

In automotive examples, the article 10 may aid in the elimination ofink/frit applied to the edges of laminated glazing panels to provideultraviolet protection of the sealants used in the lamination processand conceal the glue seam from view. With the disclosed method 50 ofmaking the article 10, gradient tinting and edge shading can beachieved, which could serve as an ultraviolet-blocker and also foraesthetic purposes. In ophthalmic lens examples, gradient tint and colorcan be achieved without using conventional films which may be expensiveto apply and subject to scratching.

Fourth, as the compositions of the article 10 disclosed herein differfrom the known copper-, silver-, and gold-doped glasses, the color ofthe articles 10 can be widely tuned without changing composition andsuccessfully meet optical specifications over a number of distinctcolors. As such, the family of compositions disclosed herein for thearticle 10 may offer a practical solution to streamlining coloredarticle production. As explained above, a wide range of opticalabsorbance may be achieved by varying heat treatment time andtemperature after forming. As such, a single tank of glass may be usedto continuously produce articles 10 that can be heat treated to multiplespecific colors as customer demand dictates (i.e., reducing productiondowntime, decreasing unusable transition glass). Further, variouscompositions of the article 10 are also capable of producing a nearcomplete rainbow of colors by varying heat treatment time andtemperature across the article 10 (e.g., a rainbow of colors can beproduced within a single article). In addition to changes in color, aperceived tint, or transmittance, may be varied across the article 10.As the tint of the article 10 itself may be adjusted, dyed plasticlaminates, films, or dyed polycarbonate lenses of conventional articlesmay be eliminated. Further, as the colors, reflectance and/or tintsachieved by the article 10 are a property of the article 10 itself, thearticle 10 may exhibit greater environmental durability (e.g., abrasionand/or chemical resistance) than conventional polymer articles. Inspecific applications, the article 10 may be utilized as sunglass lenses(i.e., which may be advantageous as the article 10 may offer a widevariety of colors in addition to absorbing infrared radiation to protectsunglass wearers from heat and the radiation) and/or in automotive orarchitecture applications (e.g., where gradient fades or multiple colorsare desired in the same window pane providing designers a new level offlexibility with respect to multiple colors, transmission, andsaturation in a monolithic article 10 all while blocking deleteriousultraviolet and/or infrared radiation thereby decreasing the heating andcooling loads on the cars or buildings they adorn). For example, thearticle 10 may meet the standards ISO 14 889:2013 & 8980-3 2013, ANSIZ80.3—2001, AS 1067—2003 and ISO 12312-1: 2013.

Fifth, as the articles 10 may exhibit tunable optical properties (e.g.,color, transmittance, etc.) with varying thermal processing, treatmentin a gradient furnace or under infrared lamp can produce nearly acomplete rainbow of colors within a single piece of material (e.g.,which may be desirable for aesthetic purposes such as cell phone ortablet backs). Further, as the thermal processing may be localized(e.g., through use of a laser), the article 10 may be patternable andcolorable. For example, a laser-assisted heating and/or cooling processmay utilize different wavelengths to produce novel decorative materialsand rapidly produce logos and images within the article 10. Byoptimizing laser power and writing speed, a host of colors can beachieved. Further, laser patterning with multiple wavelengths may beemployed to selectively bleach (i.e., remove color and/or tint inselected areas through the dissolution and of the chemical alteration ofthe precipitates) which may be useful for decoration, gradientabsorption, or other unique artistic effects.

EXAMPLES

The following examples represent certain non-limiting examples of theglass-ceramic materials and articles of the disclosure, including themethods of making them.

Referring now to FIGS. 3A and 3B, provided are images of three pieces ofglass-ceramic wafer (e.g., the substrate 14) denoted as samples 1, 2 and3. Samples 1, 2 and 3 had the composition outlined in Table 6.

TABLE 6 Constituent Mol (%) SiO₂ 55.4061 Al₂O₃ 10.8486 B₂O₃ 12.6679 Li₂O5.4285 Na₂O 6.6304 K₂O 0.0230 MgO 0.0148 CaO 0.1906 SnO₂ 0.1428 WO₃3.0956 Ag 0.1160 Fe₂O₃ 0.0023 Cl— 0.0008 TiO₂ 0.0040 F— 5.4287 Total 100

Samples 1, 2 and 3 were placed on a piece of cellular ceramic such thatsample 1 did not contact samples 2 and 3, and such that sample 2partially covered sample 3. Samples 1-3 were then plunged (e.g., step58) into an ambient air electric oven pre-heated to 550° C. and held forapproximately forty minutes. Samples 1, 2 and 3 were removed from theoven on the piece of cellular ceramic and allowed to cool in ambientair. Only where sample 2 overlapped with sample 3 did a tinted area 70having a strong red coloration develop. The experiment demonstrates thatby altering the cooling rate of the samples (e.g., by using sample 2 asa thermal blanket over a portion of sample 3), that a significant changein optical absorbance can be observed. Without being bound by theory, itis believed that the tinted area 70 is the result of the higher thermalmass of overlapped samples 2 and 3 cooling slower and resulting in agreater volume and average size of crystalline precipitate.

Referring now to FIGS. 3A-3D, provided are absorbance spectra in OD/mmof sample 2 (FIG. 3C) and sample 3 (FIG. 3D). Regions “A” and “C” (e.g.,the first portion 34) were sections of samples 2 and 3 which were notcontacting each other. Regions “B” and “D” (e.g., the second portion 38)were in direct contact with each other and form the tinted area 70 ofeach of sample 2 and sample 3.

Referring now to FIGS. 4A and 4B, provided are images of a glass-ceramicwafer made of the composition outlined in Table 6. In FIG. 4A, the waferis cooling in air on a lab bench after thermal treatment at 550° C. inan ambient air electric oven for approximately 60 minutes with variousstainless steel washers and nuts (e.g., heat sinks) placed atop it. Thewafer was then allowed to cool in ambient air. Note that as the wafercools, the regions around the washers and nuts is initially lighterbecause the washers and bolts are holding the heat longer above thetemperature where the color generating crystallites form. As the wafercools further, the regions around and beneath the washers and nutsappears darker. In FIG. 4B, the fully cooled, room temperature wafer isplaced on a light table to highlight the difference in optical density.

Referring now to FIG. 4C, provided is a plot of temperature vs time toillustrate the cooling rate of the wafer of FIG. 4A incorporating awasher. The plot of FIG. 4C was formed using the same composition asTable 6 and thermal treatment (550° C. for 1 hour and then cooling inambient air) as FIG. 4A. During cooling, thermocouples were affixed tomeasure the temperature of the wafer not contacting a metal washer(i.e., denoted “wafer” on FIG. 4C) and the wafer contacting the washer(i.e., denoted “washer” on FIG. 4C). As self-evident from the data, theportion of the wafer contacting the metal washer cooled more slowly. Thewafer itself cooled at a rate of about 1.04 degrees C. per second andthe wafer contacting the metal washer cooled at 0.649 degrees C. persecond (i.e., about 1.6× slower). Such a lower cooling rate associatedwith the presence of the metal washer is believed to have increased thesize and quantity of the crystallites which in turn generated theoptical pattern observed in FIG. 4B.

Referring now to FIGS. 5A and 5B, provided are images of a wafer made ofthe composition of Table 6. FIG. 5A is an image of the wafer cooling inair on the lab bench after thermal treatment at 550° C. in an ambientair electric oven for approximately 60 minutes with a cylindricallyshaped graphite part placed atop the wafer prior to thermal treatment.Similarly to what was observed in FIG. 4A, the region around thegraphite heat initially remains transparent (FIG. 5A) because thegraphite acts as a heat sink, allowing the glass to remain above thetemperature of color generation. Again, as the part cools, the regionbelow the graphite part darkens (FIG. 5B). Note that despite it being ahollow/ring-shaped form, the resultant coloration does not reflect theactual shape of the part. Without being bound by theory, it is believedthat the resultant shape is a due to the large thermal mass of the partand by the diffusion of the heat from the graphite part.

Referring now to FIGS. 6A and 6B, provided are images of a wafer made ofthe composition of Table 6. FIG. 6A is an image of the wafer cooling inair on the lab bench after thermal treatment at 550° C. in an ambientair electric oven for approximately 60 minutes with two stainless steelwashers placed atop the wafer prior to thermal treatment. Upon coolingin ambient air analogous behavior to what was observed in FIGS. 4B and5B, however by removing the washers after a few seconds after the waferwas removed from the oven, the resulting darkening pattern had greaterresolution.

Referring now to FIG. 7A, provided is an image of three wafers made ofthe composition of Table 6. Thin (i.e., about 0.5 mm) galvanized metalletters (e.g., the heat sink and/or the infrared shield) were placedatop the three wafers before heat treatment, followed by approximately1.5 hours at 550° C. in an ambient air electric oven, and then coolingin ambient air. The resolution was improved due to the reduced thicknessof the metal heat sink, which reduced thermal diffusion.

Referring now to FIGS. 7A and 7B, provided in a plot of the absorbancespectrum in

OD/mm between a region that was not in contact with the metal letter G,denoted by “E” (e.g., the first portion 34), and a second region thatwas beneath the metal letter G denoted by “F” (e.g., the second portion38).

Referring now to FIGS. 8A and 8B, provided are images of wafers made ofthe composition of Table 6. Aluminum foil layers (e.g., the infraredshield) have a similar effect as what was shown in FIG. 7A. The depictedexamples, the wafers were wrapped in Reynolds® aluminum foil and heattreated at 550° C. for about 60 minutes and cooled in ambient air (FIG.8A). FIG. 8B shows the result of aluminum foil strips of varyingthickness being wrapped around a wafer with the same composition andthermal treatment. In both parts, regions covered with the aluminum foil(e.g., the second portion 38) were significantly darker than theuncovered regions (e.g., the first portion 34). Without being bound bytheory, it is believed that owing to the low thermal mass of aluminumfoil, the change in optical absorbance is a result of the aluminum foilfunctioned as an infrared reflector that slows the cooling rate of thewafer which is emitting in the infrared as it cools.

Referring now to FIG. 9A, provided is an image of a wafer made of thecomposition of

Table 6. The use of a metal nut (e.g., a heat sink) can also act toretard or completely prevent coloration of the wafer within the regionit contacts by preventing that local area from reaching thecrystallization temperature. For example, by placing a metal nut ontothe wafer and heat treating the wafer for a shorter amount of time (1-30minutes) followed by rapid cooling, the metal nut may prevent the waferfrom reaching the crystallization temperature. As the metal nut heatsslower than the wafer on which it is positioned, the region beneath themetal nut remains cooler than the rest of the material which slows theformation of color generating crystals in that region. The wafer of FIG.9A was heat treated for 7 minutes at 600° C., and cooled in ambient air.The approximate region where the metal nut was placed remained largelytransparent.

Referring now to FIGS. 9A and 9B, provided is an absorbance spectra inOD/mm of the light-colored region that was directly contacting the metalnut, denoted as “G”, and the darker colored region of the sample thatwas not contacting the metal nut, denoted as “H”.

Referring now to FIG. 10A, provided in FIG. 10A in an image of a waferhaving the composition provided in Table 6. The wafer was treated in thefollowing manner: (1) two stainless steel washers were pre-heated to700° C. in an ambient air electric oven; (2) simultaneously, a pieceun-annealed wafer was placed into an ambient air electric furnaceholding at 550° C. for 5 minutes; (3) the 700° C. washers weretransferred onto the pre-heated wafer and held at 550° C. for 5 min; (4)the wafer was then removed from the oven, the washers were taken off thesurface, and then the wafer was heated for another 5 minutes at 550 C;and (6) upon cooling in air, an image of where the washers were placedappeared within the wafer. Such a thermal treatment indicates that ifthe temperature of a heat sink placed on a wafer is at or above thecrystallization temperature and locally raises the temperature of aregion of the wafer it is placed upon, it can also be used toselectively crystallize a particular region (i.e., like a brandingiron).

Referring now to FIGS. 10A and 10B, provided is an absorbance spectra inOD/mm of the light-colored region that was not contacting the metalwasher, denoted as “I”, and the darker colored region of the sample thatwas contacting the metal washer, denoted as “J”.

Referring now to FIG. 11A, similarly to FIG. 10A, provided is anadditional example of the technique described in connection with FIG.10A. Pictured is a wafer having the composition of FIG. 10A that wastreated in the following manner: (1) the wafer was placed in an ambientair electric furnace for 10 minutes that was pre-heated to 550° C.; (2)simultaneously, a stainless steel washer was pre-heated to 700° C. in asecond an ambient air electric furnace; (3) the pre-heated washer wasremoved from the furnace and placed atop the wafer and further heated at550° C. for an additional 10 minutes; (4) the wafer with the washer atopit was removed from the oven; and (5) the washer was then immediatelyremoved from the surface, and the wafer was allowed to cool in ambientair. The region of the wafer where the washer was in contact was red incolor, versus that which was not in contact was an amber brown color.

Referring now to FIGS. 11A and 11B, provided is an absorbance spectrumin OD/mm of an amber brown-colored region that was not contacting thesteel washer denoted by “K” and a red-colored region that was directlybeneath the metal washer, denoted by region “L”.

Referring now to Table 7, provided are a variety of optical propertiesof the Examples provided in the plots of FIGS. 3C, 3D, 7B, 9B, 10B and11B.

TABLE 7 Average Visible Average Near- Absorbance Infrared Absorbance(OD/mm from (OD/mm from FIG. Region 400-750 nm) 750-1500 nm) 3C A 0.300.04 3C B 49.38 0.08 3D C 0.30 0.04 3D D 17.66 0.09 7B E 0.24 0.05 7B F0.63 0.09 9B G 0.07 0.03 9B H 0.77 0.45 10B I 0.13 0.07 10B J 0.18 0.2511B K 0.29 0.35 11B L 0.63 0.69

Table 8 provides the Contrast Ratio of the average visible (400-750 nm)and near-infrared (750-1500 nm) absorbance in OD/mm of Region 2/Region 1(e.g., the second portion 38 divided by the first portion 34). The valueof the Contrast Ratio conveys the change in absorbance manifested fromthe selective crystallization.

TABLE 8 Visible Contrast Ratio Near-Infrared Contrast Ratio FIG. (OD/mmfrom 400-750 nm) (OD/mm from 750-1500 nm) 3C 162.55 1.84 3D 58.44 2.057B 2.61 1.94 9B 11.16 13.20 10B 1.41 3.42 11B 2.15 2.00

Referring now to FIGS. 12A-14B, provided are additional examples ofglass-ceramic wafers made of the composition outlined in Table 6. Theglass-ceramic wafers were subject to thermal processing to provide aplurality of portions with different optical properties (e.g.,transmittance, color, optical density, etc.), thereby providing agradient tint in the wafer. In these embodiments, a hybrid thermal heatsink comprising an IR-reflective coating and an insulating core ofvarying shape was used to alter the local temperature of the wafers,which altered the optical absorbance of the wafers. The heat sinks wereplaced in direct contact or proximity to the glass ceramic wafer at roomtemperature and then the entire assemblage was heat treated together, asalso discussed above with regard to other embodiments. The portions ofthe glass that were in direct contact or proximity to the heat sinkremained cooler than the exposed portions and, thus, resulted in adifferent optical absorbance. Varying the shape and size of the heatsink enables control over how much of a temperature delta exists betweenthe region affected by the heat sink. Further the heat sink shape can beused to create unique patterns or gradients in color with a conventionalisothermal annealer or ‘lehr’.

Without being bound by theory, the superior performance of these hybridheat sinks is attributed to the combined use of a broadband infrared(IR) reflector that rejects heat and an insulator, which has low thermalconductivity. This combination of reflection and poor heat transferenables the area of the glass ceramic affected by this hybrid heat sinkto remain cooler for a longer duration of time during heat treatmentthan with other heat sinks made from single materials (e.g., a metal ora refractory block).

As shown in FIGS. 12A and 14A, hybrid heat sinks of varying shape andsize enable the creation of gradient tint and colored glass, for examplegradient tint and colored sunglasses. Conventionally, such graded lensesare manufactured by laminating an organic film with a gradient in tintor color between two glass plies and with coatings applied to the glasssurface. The embodiments disclosed herein develop the gradient tintwithin the glass, as compared to the conventional methods that developthe tint exterior of the glass. The embodiments disclosed hereintherefore have the advantage of not being susceptible to scratching andeliminating the need for lamination, thus reducing cost.

The gradient tint lens shown in FIG. 12A was created by placing anun-ceramed lens blank into a refractory holder and setting the ‘hybrid’heat sink with a sillimanite core over approximately half of the lens.The heat sink assemblage rested on a metal lens carrier and was not indirect contact with the lens. To further slow the heat transfer, a pieceof aluminum foil cut to resemble a half-circle was placed on theopposing surface of the lens that was beneath the heat sink, thisproviding infrared reflectivity on both surfaces of the lens. The entireassembly was heat treated by placing it in, for example, a pre-heatedoven at about 510° C., holding at that temperature for about one hour,cooling to about 425° C. at 1° C. per minute, and then cooling to roomtemperature at furnace rate. Optical absorbance measurements werecollected at various regions of the 1.9 mm thick lens to demonstrate thegradient of color that this treatment produced (see FIG. 12B). At thetop of the sample (denoted in FIG. 12A), the lens was dark blue, whichgradually faded to a lighter blue, then to a blue-green, and finally toa yellow. Average ultra-violet (UV), visible (VIS), and near-infrared(NIR) transmittance for the different regions is shown in Table 9.

TABLE 9 Average Transmittance (%) Wavelength 1. 2. Inner 3. Inner 4.Yellow Range (nm) Blue Edge Dark Blue Yellow Edge 200-380 0.05 0.01 0.80  1.20 380-750 4.40 9.72 53.26 22.32  750-2000 0.70 2.82 45.5910.79

One exemplary embodiment of a heat sink design that is highly effectivefor the creation of gradient tint and gradient colored objects iscomprised of a sillimanite refractory core 100 (about 6 cm×2.5 cm×2.5 cmin size) that is wrapped in ⅛″ thick Kaolin wool (e.g., Fiberfrax®) andthen enveloped in aluminum foil (approximate thickness 0.016 mm), asshown in FIGS. 13A-13E. The sillimanite and Kaolin wool serve as theinsulating core and the aluminum foil provides broad-band infraredrejection, thus reflecting much of the heat away from the surface of thelens. Fused silica was also substituted for sillimanite as the corematerial in some embodiments and provided similar results. Therefore, itis contemplated that any material with a thermal conductivity between1.4 and 1.6 W/m/K is suitable as a core for these hybrid heat sinks.

As shown in FIGS. 13A and 13E, in some embodiments, the aluminum foilwas twisted to make a point at the top of the heat sink. To provideinfrared reflectivity on the bottom side of the lens, a circular pieceof aluminum foil was placed in the bottom of a lens holder 110 (FIG.13C) and then the lens was placed atop it (FIG. 13D).

In one exemplary process, the heat sink shown in FIGS. 13A and 13B wasthen placed in the center of the lens blank in direct contact with thelens (FIG. 13E). The assembly was then heat treated by placing it afurnace pre-heated at, for example, about 550° C., holding at thattemperature for about fifteen minutes, cooling to about 425° C. at 1° C.per minute, and then cooling to room temperature at furnace rate. Asshown in FIG. 14A, optical absorbance measurements were collected atvarious regions of the 1.9 mm thick lens to demonstrate the range ofcolor that this treatment produced (see FIG. 14B). As shown in FIG. 14A,this heat sink resulted in concentric gradient color. The outer edge ofthe lens was red. Closer in from the edge the color shifted to a darkyellow, and then to a dark blue. The center of the lens was a lightblue. Average ultra-violet (UV), visible (VIS), and near-infrared (NIR)transmittance for the different regions is shown in Table 10.

TABLE 10 Average Transmittance (%) Wavelength 1. Outer 2. Inner 3. InnerDark 4. Light Blue Range (nm) Red Edge Yellow Ring Blue Ring Center200-380 0 0.05 0.06 0.09 380-750 40 6.17 4.72 6.26  750-2000 50.15 3.710.7 1.26

It is also important to note that the construction and arrangement ofthe elements of the disclosure, as shown in the exemplary embodiments,is illustrative only. Although only a few embodiments of the presentinnovations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multipleparts, or elements shown as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures, and/or members, or connectors, orother elements of the system, may be varied, and the nature or number ofadjustment positions provided between the elements may be varied. Itshould be noted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present innovations.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the desired andother exemplary embodiments without departing from the spirit of thepresent innovations.

It will be understood that any described processes, or steps withindescribed processes, may be combined with other disclosed processes orsteps to form structures within the scope of the present disclosure. Theexemplary structures and processes disclosed herein are for illustrativepurposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can bemade on the aforementioned structures and methods without departing fromthe concepts of the present disclosure, and, further, it is to beunderstood that such concepts are intended to be covered by thefollowing claims, unless these claims, by their language, expresslystate otherwise. Further, the claims, as set forth below, areincorporated into and constitute part of this Detailed Description.

What is claimed is:
 1. A method of forming a glass-ceramic article, comprising: forming a substrate having a substantially homogenous glass composition, wherein the substrate comprises a first portion and a second portion; and variably crystallizing at least one of the first and second portions of the substrate to form a plurality of crystalline precipitates within the at least one of the first and second portions, wherein the variably crystallizing of the at least one of the first and second portions results in at least one of: (a) a difference in absorbance between the first and second portions of 0.04 OD/mm to 49 OD/mm over a wavelength range of from 400 nm to 750 nm, and (b) a difference in absorbance between the first and second portions of 0.03 OD/mm to 0.69 OD/mm over a wavelength range of from 750 nm to 1500 nm.
 2. The method of claim 1, wherein the step of variably crystallizing further comprises thermally processing the first and second portions of the substrate at different temperatures.
 3. The method of claim 1, wherein the step of variably crystallizing further comprises thermally processing the first and second portions of the substrate at the same temperature and cooling the first and second portions at different cooling rates.
 4. The method of claim 1, wherein the step of variably crystallizing further comprises increasing the temperature of the first and second portions at different heating rates.
 5. A method of forming a glass-ceramic article, comprising: forming a substrate having a substantially homogenous glass composition, wherein the substrate comprises a first portion and a second portion; and thermally processing the first and second portions of the substrate at one or more of (a) different temperatures, (b) different heating rates and (c) different times, wherein the thermally processing step is conducted to generate a plurality of crystalline precipitates in at least one of the first and second portions of the substrate such that (i) a difference in absorbance exists between the first and second portions of 0.04 OD/mm to 49 OD/mm over a wavelength range of from 400 nm to 750 nm and (ii) a Contrast Ratio between the first portion and the second portion is from 1.4 to 165 over a wavelength range of from 400 nm to 700 nm.
 6. The method of claim 5, wherein the glass-ceramic article further comprises WO₃ from 0 mol % to 15 mol %.
 7. The method of claim 6, wherein the WO₃ is from 0 mol % to 7 mol %.
 8. The method of claim 5, wherein the glass-ceramic article further comprises MoO₃ from 0 mol % to 15 mol %.
 9. The method of claim 8, wherein the MoO₃ is from 0 mol % to 7 mol %.
 10. The method of claim 5, wherein the step of thermally processing the first and second portions of the substrate is conducted such that the first and second portions are subjected to a temperature greater than 400° C. for different times. 